PLEASE NOTE: THIS PROJECT IS NOT SCIENTIFIC. IT IS A HOBBY.
"I was looking for information on an old mammal and found this lot. What is this
project?"
It's got lots of information on old mammals. For a short bit of background information, see
here.
Looking for books?
You could visit the
Book Centre and look around.
These groups are
marusupials (or close relatives) from the days of the
dinosaurs. Generally, they were inhabitants of North
America. The scheme I'm presently following is that of Case et al, 2004. They place both families
within the cohort of Alphadelphia. This view is not
universally followed. I happen to presently find it useful for purely bookkeeping reasons.
For those of a technical persuasion, the two families are united within the Archimetatheria
Szalay, 1993.
Mammalian butchers
Stagodontid molars were made for cutting meat, (Kemp 2005, p.198). A carnassial notch is
located on the crest between the protoconid and
metaconid cusps of lowers. This is a feature much favoured
by carnivorous mammals.
Semi-aquatic stagodonts?
The Society of Vertebrate Paleontology Abstracts for their 2004 meeting includes the
following: Longrich N, Aquatic Specialization in mammals from the Late Cretaceous of North
America. It's a somewhat different interpretation of this family.
A number of tail bones were found in the collection of the Royal Tyrrell Museum in Canada,
and they had come from Campanian strata of Alberta. These
vertebrae are unusually long, (1.4 to 2.5cm), and wide. They resemble the bones from
beavers and platypussies, and both enjoy a good swim. Furthermore, they come from river
deposits.
The only appropriately sized genus known from the location is the stagodont Eodelphis.
If this is indeed part of its tail, then there's a good chance it also liked splashing
around. The teeth of Didelphodon have previously been compared to those from sea otters,
(Enhydra). Consequently, the suggestion is this family possessed aquatic
adaptations. An animal with the tail still on it would be appreciated by all.
Objection
Fox & Naylor, 2006 don't swim along with this possibility (p.28-29). They point out
that referrals of postcranial material based purely on size aren't conclusive. Other
contemporary mammals (therians and
multituberculates) reached similar sizes. The fact that the remains were from river
deposits is hardly surprising. At least most North American fossil sites of this age were
produced by river action. Stagodonts may not be to blame for these vertebrae. They
certainly haven't been found guilty. |
A. Stagodontidae B. Pediomyoidea
| Taxon: Stagodontidae Marsh OC, 1889
The following is
based largely upon my reading of Fox & Naylor, 2006.
Beware of the stagodonts
Stagodonts were marsupials (or near relatives) from
the late days of the dinosaurs in North America (p.13). The first remains were welcomed
from Wyoming in 1889. Not much is known beyond teeth and partial jaws, but that's enough
to show some stagodonts were among the largest mammals
around, and the authors enlist a smallish cat as a comparison for the size of the biggest,
Didelphodon vorax. The family doesn't seem to have survived
the mass-extinction(s) at the end of the Cretaceous.
Eodelphis was a generally earlier and less mighty version,
but it was still a giant among the mammalian midgets, and some of those presumably counted
among its victims. These critters were thugs armed with specialised teeth for crushing and
carnivory. If a waiter had approached with a plate of tasty Cretaceous salad, then a
stagodont would've shown more interest in biting the hand that attempted to feed it.
Missing bodies
Various bits of skeleton have sometimes been referred to members of the clan but, as yet,
they've not been found in articulation with diagnostic fossils. The sizes may be about
right, though they could belong to other larger mammals. The oldest definite traces are
isolated molars of Eodelphis from Alberta, which are
something like 83.5 million years old. The Dinosaur Park Formation of Alberta offers more
generous fossils for the same genus, and these are a bit more recent; around 75 Mya (p.14).
Two species have been distinguished there, with the differences concerning proportions of
teeth and dentary. A toothless jaw from the Maastrichtian
of Montana could also be a late occurrence of this genus, although this is presently
uncertain.
Didelphodon seems to have taken over the family business in the Maastrichtian, and
fossils are widespread in the Midwest. At least three species were prowling around. None
managed to prowl on into the Paleocene, RIP.
Stagodont power
Stagodonts were mean hoods with streetwise dental adaptations; armed muggers and presumably
sneak thieves of carrion. The molars are both proportionately large and robustly built.
The trigonid is squashed towards the front of the crown
with a tall, blade-like paraconid almost equalling the
protoconid in height. A crest, the paracristid, carries
a carnassial notch; a dismembering tool beloved by carnivorous mammals. The third
traditional trigonid cusp, the metaconid, has been
reduced.
The uppers have a strong metacone and a small paracone. The postmetacrista crest is elongated
and high, whereas the preparacrista is short. Along with other details, the ancestral
therian strong prevallum/postvallid shear had been reduced in
favour of postvallum/prevallid shear. These teeth cut in a specialised, stagodont way.
The molars were ready for action when freshly erupted. With use, however, the features of
the crown wore down, and this transformed them into powerful crushing, grinding devices.
As with other contemporary metatherians, the wear began
with the front molar and then worked its way back along the line.
Where known, stagodont premolars are also large, crushing
teeth. They appear to increase in size through the generations. Premolars (P3 and p3) are
larger in Eodelphis cutleri than E. browni. All Didelphodon premolars
feature truly enlarged crowns; scrap yard wreckers for dealing with tough, profitable junk
such as bone and shell.
These aren't teeth for lovers of elegance and artistry. Stagodont style relied upon brute
force. If only they'd been ten times bigger or so, Tyrannosaurus may not have had
to wait so long for extinction.
Fee-fi-fo-fum,
I smell the blood of a chameleon,
Be it alive or be it dead,
I'll grind its bones to make me fed.
Non-stagodonts
A number of possible allies for stagodonts have been proposed, although Fox and Naylor seem
less than impressed with their credentials in this regard.
An early applicant is Pariadens kirklandi from
the Cenomanian of Utah. They were even less keen on the 'sister'
taxon, which they publicly denigrate as "P. mckennai". They see it as some
kind of presently indeterminate therian. Boreodon is
deservedly humiliated with the term nomen dubium. (Should anybody be looking for it, I list
it as a synonym for Eodelphis cutleri.)
Delphodon (a collection of teeth) fares little better.
Lowered replacement
Marsupials aren't keen on replacing teeth. All are primary teeth excepting for the final
premolars, p3 or P3. As this trait is universal among all living representatives, it
presumably also characterised the near relatives of marsups as well.
Traditionally, many Cretaceous American metatherians
were categorised as didelphids, the family which includes the various American opossums.
Among extant members, the last lower postcanines to
erupt are the p3 and m4. It'd be nice to know if the Cretaceous critters were following
the same rules.
A juvenile Didelphodon dentary interviewed by Clemens in 1966 was at least
consistent with the possibility (p.26). There were no signs of replacement for the first
two premolars, while the third wasn't fully erupted (p.27). Further back along the tooth
row, m1 and m2 were completely in place and the third molar was erupting. The m4 was
comparatively developmentally retarded. Similar evidence exists for
Alphadon eatoni, a non-stagodont.
Fossils described by Fox and Naylor also comply. A lower jaw of Didelphodon coyi
shows the first two premolars are heavily worn, but the third is more pristine and not fully
erupted. The two remaining molars behind had already seen much service as well. The
holotype, a different specimen, has an unworn p3, a moderately worn m3 and a slightly worn
m4. The other two molars declined to be interviewed.
Where evidence is available, American Cretaceous metatherians conform to expectations
based on extant marsupial eruption and replacement habits.
(An appeal for sympathy: A freak washing up accident involving a dried-on noodle and my
finger nail, made typing those last 250 words bloody painful.)
Link:
Acta Palaeontologica Polonica 2006, 51(1), p.13-36
http://app.pan.pl/acta51/app51-013.pdf
Fox & Naylor, 2006 is presently freely accessible on-line in pdf format.
Genera: Boreodon (= Eodelphis), Cimolestes sp. (= Didelphodon /
Eodelphis), Delphodon, Diaphorodon
(= Didelphodon), Didelphodon (also partly =
Delphodon), Didelphops (= Didelphodon), Ectoconodon
(= Didelphodon), Eodelphis,
Pariadens, Stagodon (= Didelphodon), Thlaeodon
(= Didelphodon), other reports
Time-Line:
Upper Cretaceous: Delphodon, Didelphodon, Eodelphis,
Pariadens, Utah |
| Genus: Delphodon Simpson GG,
1927
Aka : Didelphodon (partly)
| Reassigned species: D. praesagus Russell, 1952 (partly) see
Turgidodon praesagus | |
| Species: | Delphodon comptus Simpson GG, 1927 |
| Aka: | Didelphodon comptus Marsh, 1889 |
| Place: | |
| Continent: | North America |
| Age: | Maastrichtian, Upper Cretaceous |
| Remarks: | Information has come to hand from Fox & Naylor,
2006 (p.15). While they provide a reference for Simpson, 1927, the paper cited doesn't
mention this genus. I just checked.
Thrilling
The genus was based on a collection of metatherian teeth.
Although McKenna & Bell included it in Stagodontidae in 1997, the specimens may well
represent Pediomys or
Alphadon.
Additional notes
Elusive. A type fossil, Didelphodon comptus Marsh, 1889 is listed in the Peabody
on-line catalogue, Yale. It's a lower molar which hasn't necessarily been reassigned.
After interrogation, its former colleague, YPM11829, confessed the following: "I was
Didelphodon comptus Marsh, 1889, then Didelphops comptus, not verified, until
I became Delphodon comptus Simpson, 1927. I then transformed myself into
Pediomys sp., Alphadon rhaister? not verified, Pediomys hatcheri
(Osborne, 1898), and now am happier as Pediomys florencae Clemens WA, 1966." |
| Reference: | |
| Species: | Delphodon praenuntius Russell L, 1928 |
| Place: | |
| Country: | |
| Age: | |
| Remarks: | Very elusive. |
| Reference: | |
| Genus: Didelphodon Marsh
OC, 1889
Aka: Diaphorodon Simpson, 1927; Didelphops Marsh, 1889;
Ectoconodon Osborn, 1898; Ectonodon (misspelling attributed to Piveteau
(1961, Traité de Paleontol. 6(1):599), Stagodon Marsh, 1889; Thlaeodon Cope,
1892
Remarks: This was one of the larger Mesozoic mammals, reaching about
badger-sized,
(though perhaps fox
might be nearer the mark). There are a couple of hundred sites featuring this genus, though
most are variations on the first link. An average length of molars is around 6mm, (Kemp
2005, p.198).
Uncertainty
Simpson assigned material to a species called Ectoconodon montanensis in 1927. As I
don't know whether this species has been transferred elsewhere, I've included an entry for
it with that name below. It may or may not be part of Didelphodon.
Stagodon
On page five Simpson states that Stagodon was freqently used for 'didelphodontin'
premolars of a heavy build.
| Reassigned species: part of D. comptus Marsh, 1889 see
Delphodon comptus; D. ferox Marsh, 1889 see D.
vorax | |
| Links:
Dino Fact File, the BBC
http://www.bbc.co.uk/dinosaurs/fact_files/volcanic/birds_mammals/didelphodon.shtml
This genus recently enjoyed an acting career, appearing in Walking with Dinosaurs.
Tim Christopher Donnell
http://www.tim-donell.de/Dinosaurier/Auswahl/Raubsaurier/raubsaurier.html
The work of Hr Donell, aged ten, (German). He shows more originality than many, especially
by placing Didelphodon into Dinosauria. It’s a nicely laid out page, which requires
attention to detail. He’s got plenty of time to take care of that.
Pteranodons by Eric Rodney Vondell (Trlafy)
http://elfwood.lysator.liu.se/libr/r/o/rodney2/rodney2.html
The log of the SS Warpspeed reports on a regurgitated Didelphodon.
Diaphorodon Archer, 1869
http://taxa.soken.ac.jp/WWW/PDB/Images/Sarcodina/Diaphorodon/index.html
As we doubtless all know, not only is Diaphorodon Simpson, 1927 a junior synonym of
Didelphodon, it also appears to be preoccupied by a genus within Pseudodifflugiidae,
which are amoebas of some kind. (With thanks to the Protist Information Service.)
|
| Species: | Didelphodon vorax Marsh OC, 1889 |
| Aka: | Cimolestes curtus Marsh, 1889; Diaphorodon curtus
(Simpson, 1927); D. ferox Marsh, 1889; Didelhops ferox Marsh, 1889;
Didelphops vorax Marsh, 1889; Ectoconodon petersoni Osborn,
1898; Ectoconodon montanensis Simpson, 1927; Ectonodon petersoni;
Stagodon tumidus Marsh, 1889; Stagodon validus Marsh, 1892 |
| Place: | Wyoming, Montana, North Dakota, ?South Dakota & Alberta,
Saskatchewan |
| Country: | USA & Canada |
| Age: | Maastrichtian, Upper Cretaceous |
| Remarks: | Lofgren, 1995 provides information on a number of
specimens collected from
McGuire Creek localities in Montana (p.111).
Various jaw fragments and isolated teeth were recovered from McGuire Creek localities in
Montana, and all but one site seem to be Paleocene in age, judging by the associated pollen
fossils. However, these were in river channels that had cut down into fossil-yielding
Cretaceous strata, and probably got mixed in by reworking.
Postcanine lengths
These all apply to McGuire Creek specimens, with several being approximations. In all cases
only a single tooth is mentioned for each position. That doesn't necessarily mean that's
all that was found.
Uppers: Premolars: P2 5.74mm, P3 6.42mm;
Molars: M1 4.37mm.
Lowers: premolars: p1 4.70mm, p2 5.71mm, p3 6.04mm, dp3 3.76mm; molars: m2 5.36mm.
The uppers are wider than long whereas, generally, the length is the greater for lowers.
However, that doesn't apply for p1. The isolated McGuire Creek teeth are similar to fossils
from the Lance Formation of Wyoming excepting for the first lower premolar. That's a bit
larger in this case. Nevertheless, it does fall within the known size range for the
species as a whole.
Holotype
The holotype attends the Peabody Museum, Yale. It's known to its admirers as YPM 11827 and
is an upper left molar from the Lance Formation of
Wyoming, (Hunter & Archibald 2002, p.198).
Other names
Matthew, 1916 reveals (p.488) that Cimolestes curtus was established for a lower
tooth, with similarities to the foremost molars of Eodelphis
browni. However, its metaconid is further reduced, the
talonid is both wider and shorter, and there are differences with more minor cusps.
It's also bigger; closer in size to what Matthew termed Thlaeodon.
Didelphodon ferox was based on based on another lower molar.
Additional notes
One source cites ?Puercan, (Prehistoric Data Files). Bear the question mark in mind! One
of the Peabody specimens is utterly perverse. It’s labelled as from the Pleistocene of
Florida, (YPM 20502). Perhaps it retired there.
Gordon & Cifelli, 2003 (p.95) offers a bodyweight of 850-1910g.
Ectoconodon montanensis Simpson GG, 1927
Thanks are due to Susan Bell for this concise summary (pers. comm. 13.3.2006). Simpson
synonymized this species with E. petersoni in 1929 (Mem. Peabody Mus. Yale 3(1):
126). Piveteau inadvertently added a misspelling of the genus to the literature
(Ectonodon - 1961, Traité de Paleontol. 6(1):599).
The following is based upon my reading of Simpson, 1927. E. montanensis was based
on an upper molar from Hell Creek. The only specimen available in 1927 was wide with blunt
cusps (p.5) and, in the then used terminology, this was a crusher from the subfamily of
Didelphodontinae. The terminology has since changed.
It's a small tooth with three main cusps and a large stylar shelf on the
buccal side. There's a notch in the centre of the shelf,
and a large cusp parallel with the metacone. A further
small cusp is in a buccal position between the paracone
and metacone. That detail and "the greater development of the style external to the
metacone" prompted, in the opinion of Simpson, exclusion from the genus of
Didelphodon. (Note: McKenna & Bell, 1997 nevertheless lists Ectoconodon
as a synonym of D. -p.52.)
Two molars were celebrated by Osborn as type fossils for E. petersoni, now aka
D. vorax, and the Montana tooth failed to quite conform with either. The proportions
are different and there are contrasts in stylar development, details of cusps and so on.
As Simpson was unable to place the tooth into the existing species, he established a new
one. "It is, however, cogeneric with them with as much certainty as can be derived
from the comparison of isolated teeth."
Simpson referred a few further fossils to Didelphodontinae in 1927. Four premolars were
assigned to "Stagodon", and he used the inverted commas in the text. Two
edentulous mandibles were interpreted as ?Thlaedon sp.. All these bits and
pieces were collected from the Hell Creek Formation and stored in New York (p.5-6).
Holotype
According to Simpson, the holotype, Amer. Mus. No. 14406, is an isolated upper left
molar collected from Crookford. It should work at the
American Museum of Natural History, New York, but I'm not certain whether it's still
gainfully employed. AMNH FM 14406 is the full number, and the file card was missing from
the on-line catalogue. It's now in place. That's more than can be said of the fossil.
An inventory conducted at some time in the 1990s recorded it as absent without leave. The
lack of any illustration in Simpson's paper suggests it may have wandered away decades
ago.
The meaning of the specific name wasn't stated, but there's just a chance it has some
connection with the State of origin. |
| References: | Marsh (1889), Discovery of Cretaceous Mammalia part 1,
American Journal of Science, Series 3, 38, p.81,92.
|
| Marsh (1892), Discovery of Cretaceous Mammalia part 3,
American Journal of Science, Series 3, 48, p.249-262. |
| Osborn (1898), Evolution of the amblypods, Part I, Taligrada and
Pantodonta, Bulletin of the American Museum of Natural History, 10, p.160-218. |
| Simpson (1927), Mammalian fauna of the Hell Creek Formation
of Montana, American Museum Novitates, 267, p.1-7. |
| Species: | Didelphodon nitor (Marsh OC, 1889) Sahni, 1972 |
| Aka: | D. vorax (partly); Stagodon nitor Marsh, 1889 |
| Place: | Wyoming |
| Country: | USA |
| Age: | Maastrichtian, Upper Cretaceous |
| Remarks: | Sahni's 1972 paper is in my crowded in-tray, and
will presumably provide more information when I eventually get around to reading it.
Holotype
Osborn, 1893 reports the type fossil was a tooth, but he had his doubts about whether it
was even mammalian (p.323).
Additional notes
S. n. was once allocated to D. v., but it resigned and became D. n. |
| Reference: | Marsh (1889), Discovery of Cretaceous Mammalia. Am. J. Sci.
(3) xxxviii, p.81-92. |
| Species: | Didelphodon padanicus (Cope ED, 1892) |
| Aka: | Thlaeodon padanicus Cope ED, 1892 |
| Place: | Wyoming, Montana, S Dakota & Alberta |
| Country: | USA & Canada |
| Age: | Maastrichtian, Upper Cretaceous |
| Remarks: | The following is based upon my reading of Matthew,
1916. He felt a redescription of what was then called Thlaeodon was essential, as
the original effort contained serious inaccuracies. Even the illustration is termed
"very crude" (p.491).
The upper and lower jaws were found by Dr Wortman at some time between 1888 and 1890, but
precisely where wasn't recorded. These two elements were picked up about 30 metres from
one another, but they match up so closely that they're probably from the same individual.
Even the details of dental wear are compatible.
Teeth
Matthew gave the lower tooth formula as: ?incisors, 1
canine, 3 premolars and
probably 4 molars. Cope had opted for four premolars and
three molars.
An alveolus indicates the canine was a large tooth. Two
narrow alveoli follow for a double-rooted p1 premolar. Then come a pair of wider holes
which Cope had thought fit for two teeth. Matthew preferred a shorter, wider version of
the following premolar. The crown of the third premolar is reasonably complete, although
the top has been worn down by usage. It's a fairly simple, chubby tooth with hints of a
talonid at the rear. This pattern of premolar reflects
what was then known as 'Stagodon' validus, and could be sensibly derived from an
Eodelphis-like ancestor.
Molars
Damage obscures the original number, but it was probably four (P.494). The rear root of
the last molar suggests a tooth of modest size. The crown of only one is present, and it
was broadly similar to Cimolestes curtus (aka Didelphodon vorax), although
considerably more worn. The available jaw space is adequate for four molars, and that's
the number found in its close relatives. It's also in line with marsupial affinities.
Dentary
Most of the rear is preserved excepting for all but the base of the coronoid process and
the angular process. Cope had reported the latter element wasn't part of the jaw, but a
broken edge suggests it'd been snapped off. The front of the dentary is modest in depth,
short in length and robustly built. The foremost portion with the incisors declined to make
itself available, and that helps explain the lack of knowledge about those teeth.
Upper jaw
The opinions of Cope and Matthew are even more at odds, when it comes to the preserved
upper fragment. Cope thought it part of the right maxilla
but it's from the left. He used a cunning method for making this mistake. It involved
muddling up the front with the back.
Upper teeth
One tooth is complete while the halves of both neighbours are also in place. A further
half crown was found by the jaw. "The single complete tooth I agree with him in
identifying as P4..." (At this point I'm slightly puzzled, as marsups are notorious
for having no more than three premolars. However, there
could've been reasons as to why the third (and final) one would be termed P4. It wouldn't
necessarily imply the presence of four.) Be that as it may, the
lingual side of a further premolar is in front and half a
molar stands behind. The other disassociated half molar is
probably from that same tooth.
What remains of the partial premolar suggests this had a wide, reasonably bulbous crown
(p.495). The fully preserved one is squarer and larger. Somewhat unusually, it's fitted
with three roots including one on the lingual side. All are described as 'stout'.
The first molar is smaller. While its width is similar, the length is compressed, and the
outline of the crown is vaguely triangular, with the base of the triangle being on the
buccal margin. Wear has reduced the cusps, but evidence
remains of a couple of stylar ones. The paracone, metacone and protocone can also be
identified, although the latter is nearly eroded down to its base. What's left compares
well to what was then termed Didelphops; yet another synonym for Didelphodon.
This molar is also triple-rooted with two supporting the buccal side.
Breakage has removed any traces of further molars but the available room suggests at least
two more would've fitted, with three as a more probable option (p.496). A total of four
is presumably correct.
Marsh's Cretaceous mammals
Othniel Marsh established a luxurious array of genera and species in the late nineteenth
century, and many were based purely on teeth. That's fine, should teeth be all that's
available, but he was referring different tooth positions from at least very similar
mouths to different genera. With this approach, a single tooth row could provide stock for
a modest managarie. While being grateful for the fossils, subsequent researchers inherited
a heck of a lot of cleaning up.
Matthew thought it likely that Didelphops ferox, D. comptus, Cimolestes
curtus (and possibly others) were all parts of Thlaeodon (which is now called
Didelphodon). Stagodon validus, the front of a jaw, was a further candidate.
However, he also wrote: "But it would be a waste of time to attempt detailed comparisons
on the present data; Marsh's genera are arbitrary assemblages of teeth which evidently were
not carefully studied or compared by the describer, the descriptions, when there are any,
are of no value and so discrepant form the illustrations as to throw doubt on their
accuracy."
I think it fair to conclude he was less than impressed.
Holotype
The holotype of Cope's T. padanicus, AMNH 3013, is a lower jaw and partial upper jaw
from South Dakota, which now resides in the American Museum of Natural History, New York.
Additional notes
The molars of this
species may be larger than those of the more widespread D. vorax, (Hunter &
Pearson 1996, p.638). The main morphological differences occur in an upper
premolar -P3, (Hunter & Archibald 2002, p.198). |
| Reference: | Cope (1892), On a new genus of Mammalia from the Laramie
Formation, American Naturalist, 26, p.758. |
| Species: | Didelphodon coyi Fox RC & Naylor BG, 1986 |
| Place: | Horseshoe Canyon Formation, Alberta |
| Country: | Canada |
| Age: | early Maastrichtian, Upper Cretaceous |
| Remarks: | The following is based upon my reading of Fox and
Naylor, 2006. Some observant readers might have noticed that's 20 years too late to be
the original description. Feel free to send a copy in:
ktdykes@arcor.de.
The authors had two additional bits of lower jaw. One came from Michchi Creek (as did the
holotype), while the second was picked up for loitering at Paintearth Creek. The first is
from the right side and better preserved than the second, a piece of left
dentary. Additionally, they obtained some upper jaw from
the museum collection.
Lower teeth
Incisors and canine
A pair of small alveoli are preserved near the one for
the canine (p.23). They're both much smaller; 1.2mm and 0.5 against a width of 3.8mm.
Root remains from these three teeth are present. The available evidence indicates the
canine must've been an impressive, forwards slanting tooth. No information had previously
been available for this species.
Premolars
The first lower premolar is present with the right jaw, and that's a first for the genus.
Earlier evidence had been limited to alveoli and isolated specimens. No
diastema separates it from either the canine or the p2.
The crown is broader than long (length 2.4mm, width 2.8). The front and rear faces of the
crown look a bit as though somebody was prodding them to make hollows. These are adaptations
for enhancing the stability of the tooth row, as the front structure could interlock with a
hypothetical bulge on the absent canine, while the p2 has an anterior cusp for the other
concavity. We eucynodonts have been interlocking our
teeth with various devices since the Triassic.
This p1 is double-rooted, although these roots are labial
and lingual rather than front and rear. The former runs
nearly vertically down into the bone, while the internal one goes diagonally backwards. As
the type fossil seems to have but one alveolus for the corresponding premolar, root
numbers appear to be variable in the species. Establishing 'normality' would require a
wider sample. The second 'new' fossil isn't well enough preserved to earn a vote on this
matter.
The second premolar is considerably larger, and it's longer than wide (5.5mm against 5.0).
An articulated p2 wasn't previously known for this species. It had been put to much use as
the cuspiology of the crown is much eroded. Roots are situated at the front and back (p.24).
The p2 of D. vorax has been reported for possession of an accessory root, but there's
no evidence of the trait in D. coyi.
Premolar number three is even larger (7.3mm long and 4.7 wide). The front hosts an
impressive protoconid while the rear is graced by a
lower, unbasined talonid. The face of the protoconid is
hollowed for interlocking with the preceding tooth. This p3 has been worn, but much less
so than for its two colleagues. It's also anchored more deeply in the bone, suggesting it
may not have been fully erupted.
Molars
Two crowns are preserved as are roots for m3 and the base of me. The molar row is set
somewhat diagonally, with the course running buccal to
lingual from front to rear. These teeth also feature
snazzy mechanisms for interlocking.
The first molar is 4.8mm long with a trigonid width of 3.2
and a talonid width of 3.5. Heavy wear ha reduced the
trigonid down to the same height as the talonid. What remains of the crown forms a relatively
flat surface.
Molar number 2 is a bit bigger (5.1mm, 3.7 and 3.8). It's not quite as worn, as the trigonid
(although flat) is still a bit higher than the talonid. Two cusp stumps reveal the
positions of the paraconid and
metaconid on the lingual side and, as typical for stagodonts, the first mentioned was
much the larger of the duo (p.25).
Upper jaw
A partial right maxilla preserves the final premolar and
front two molars. Securely matching bits of isolated lower and upper jaws isn't always
possible, but it seems safe enough in this case. It clearly belongs to the genus and the
size suggests this species. Furthermore, when held against each other, the molars occlude
well.
Upper teeth
Premolar
P3 is the tallest tooth remaining and large as well (length 5mm, width 5.4). A concavity on
the front presumably accommodated part of the P2. The crown features a
labial paracone and a swollen, low lobe on the lingual
side. The top of the paracone has been worn down.
Molars
M1 is in good condition excepting for some wear. It's much like a smaller version of the
corresponding tooth from D. vorax (length 4.0mm, front width 4.6, rear 5.5). A deep
ectoflexus bay divides the
buccal side into two lobes; the parastylar and metastylar lobes. What remains of the
stylar cusps matches expectations for the genus. Cusps A and B are partly worn, there's no
C and cusp D is large yet low. A small E cusp could have been present but no traces
remain.
Most the metacone has been eroded but it was originally larger than the paracone, while the
protocone is short and wide. The buccal side of the crown is adorned with a high
postmetacrista crest, and a carnassial notch prevents this from meeting the base of the
metacone on the rear, labial portion.
The second molar is incomplete, and the width at the front was 5.5mm. It has a reduced
paracone (smaller than the styolcone), as is the stagodont style (p.26). The remains of the
metacone indicate this was larger than the paracone. The protocone is tall and well-poised
to engage with an m2 talonid below.
Holotype
The type fossil, TMP 91.166.1, is a partial right dentary in the Royal Tyrrell Museum,
Drumheller. This was rescued from Michichi Creek, Alberta.
Additional notes - the local fauna
This microvertebrate location has yielded very few mammal fossils so far. Other finds
include four indeterminate bones, a left lower Pediomys
molar, and some kind of undescribed multituberculate,
(Ryan et al 1998, p.130).
Dinosaur friends might be pleased to know about the 220 or so hadrosaurid elements, (40
baby-sized). Amongst the other represented dino taxa are Paronychodon,
Richardoestesia, Sauronitholestes and Tyrannosauridae. Oh yes, and the baby
hadrosaurid-menacing Troodon. |
| Reference: | Fox & Naylor (1986), A new species of Didelphodon
Marsh (Marsupialia) from the Upper Cretaceous of Alberta, Canada: Paleobiology and phylogeny.
Neues Jahrbuch Geol. Paläont. Abh. 172, p. 357-380. |
| Species: | Didelphodon tumidus |
| Place: | |
| Country: | |
| Age: | |
| Remarks: | Assumption: = Stagodon tumidus = D.
vorax. |
| Reference: | |
| Species: | Didelphodon validus |
| Place: | |
| Country: | |
| Age: | |
| Remarks: | Assumption: = Stagodon validus = D.
vorax. |
| Reference: | |
This is not a photo of a basal marsupial, but I suspect you
noticed. This is actually Triceratops. In the background, to the right, you might
catch a glimpse of Dimetrodon, an old-fashioned synapsid of the Permian. A rather
more advanced, mammalian therapsid can be seen in the centre of the picture. This was taken
at the Senckenberg Museum in Frankfurt, which is well worth a visit.
|
| Genus: Eodelphis Matthew WD,
1916
'dawn Delphis'
Aka: Boreodon, Cimolestes (partly)
Remarks: Weights of one to two kilos have been suggested for this genus, as have lower
figures.
Rigby and Wolberg reported on fragmentary teeth from the Kirtland Shale of New Mexico in
1987, and referred to them as cf. Eodelphis. The age is thought to be Campanian.
The following is based upon my reading of Simpson, 1951.
Matthew's 1916 description of this marsupial (or at least
metatherian) introduced the first North American
therian, which offered no room for doubt concerning its wider affinities (p.2). Prior
to this, the metatherian or eutherian credentials of all
relevant taxa were under dispute. This is partly a
consequence of the predominance of isolated teeth. To make things more fun, the lower
molars of both groups from the North American Cretaceous are
inconveniently similar. One of the most helpful distinctions concerns the cusps of the
talonid. In the metatherian version, the hypoconulid is
generally lingually situated and very close (twinned) to the
entoconid. The eutherian tendency is for that first cusps to be between the entoconid and
the hypoconid. It took time, however, for clarity to arise on these issues.
Having established Eodelphis was (in the terminology of the time) a marsupial, he
then went far too far. He decided all then known Cretaceous therian fossils were probably
marsups or, at any rate, there was nothing valid showing some to be placentals (eutherians
in this project. This seems to have been based on expectation. Despite both lineages
having existed for a broadly similar length of time, with the earliest members of both now
dating back 125 million years (Sinodelphys and
Eomaia), some modern eutherians think of themselves
as being obviously more 'advanced'. As Simpson put it, this conclusion : "... fitted
in with a widespread idea that ancient mammals should be marsupials." The
italics are used in the paper.
Untangling Cretaceous therians
This sort of view was prevalent. It was clearly falsified in 1926 by the description of
Zalambdalestes from Mongolia.
(deltatheriids were also assigned to Placentalia, but
better specimens collected in the 1990s suggest they're basal
metatherians or close relatives.) Isolated of teeth of
Gypsonictops from North America were also identified as placental, while a
couple of other genera, referred to as placnetals by Marsh in the nineteenth century, were
found to be good candidates: Batodon and
Telacodon. In contrast, some of Marsh's proposed
placentals opted to be metatherian; eg. Pediomys (p.3).
As he readily states (p.4), Simpson was capable of muddling metatherians and eutherians as
well. He was convinced Euangelistes fitted into the former gang in 1929. New
specimens provided by Paul McGraw insisted that was wrong. (It's since be synonymized with
Gypsonictops.) There's a nice note on page ten. "I am much indebted to him
for this clue and, particularly, for his courteous insistence that my serious blunder be
corrected by myself."
|
| Species: | Eodelphis browni Matthew WD, 1916 |
| Place: | Alberta & Montana |
| Country: | Canada & USA |
| Age: | Campanian, Upper Cretaceous |
| Remarks: | The following is based upon my reading of Fox &
Naylor, 2006. Their study was concerned with an upper jaw fragment. Conveniently, Matthew's
1916 paper has also become available, and that was based on lower jaw.
Upper jaw
Fox and Naylor had a new maxilla from Dinosaur Provincial
Park, Alberta (p.16). Alveoli and teeth ensured some information
was available on the left row extending from the canine to the second molar. The canine,
P3 and M2 positions were all otherwise absent.
Canine
The alveolus isn't complete but it's obviously large. It outdoes the holes for the
postcanines in this regard. As there's no indication of
subdivision, this tooth was probably single-rooted, as is the case for
Didelphodon vorax.
Premolars
P1 is small and double-rooted. No gap separates it from the canine. Stagodonts believed in
packing their teeth closely together, and had no use for wimpish accessories such as
diastemata. Not much detail remains of the worn crown, but
it was longer than wide, and rear was a bit broader than the front. The back root's larger
than its front partner and set very close to the first on P2. An apparent diastema between
those two crowns is caused by breakage and wear. The length is 1.8mm and the width is
1.5.
P2 is larger; 3.3mm long by 1.4 - 1.8 wide (front and back respectively) (p.18). This tooth
is also double-rooted and it features one main cusp; the paracone. Most surface enamel has
gone but the shape hasn't suffered all that much. When viewed from the side, the crown is
almost triangular, although the rear slope is a bit longer than the front one. There's a
cingulum both fore and aft, with the latter being wider.
They're perhaps a bit shy as they fail to meet up either
lingually or labially. In these and further ways, it's
rather like the corresponding tooth of the Virginian opossum, but the front cingulum is
stronger for the fossil genus.
Two alveoli attest to the position of the P3. They're both
larger and further apart than those anchoring the premolar in front, and this indicates a
bigger tooth. The rear alveolus is narrower than the crown of the proceeding molar, and
this contrasts to the situation with E. cutleri, in which the premolar is wider.
Molars
Only the first molar had the decency to show up. It's 3.4mm long and 3.4 to 3.9 wide
(front and back respectively). This tooth is damaged but retains its stagodont character.
There's a wide stylar shelf on the buccal flank of the crown,
and a strong stylocone and protocone. The paracone seems to have shrunk over the
generations. It's not as large as the metacone.
Handing out refutations
The partial maxilla adds further information for this species. For example, it's the first
fossil to have provided discussion on possessing a large canine, albeit a now absent one.
This was previously doubted. It also refutes accusations of the P1 being procumbent in
these animals, as this tooth is proudly vertical. E. browni denies an accusation
that the genus had a significant diastema behind the P1.
Some commentators had expected these conditions to apply (presumably by inference from
comparisons), but Eodelphis isn't guilty on any of these traits. As a consequence,
several data sets require revision.
The jaw also exhibits a rounded rim internal of the M1 molar (p.19). This looked familiar,
as the bony palate of marsupials is fitted with holes; palatal vacuities. Such gaps had been
said to be synapomorphies for crown-group marsups, but
E. browni, E. cutleri and Didelphodon vorax have all now voiced
stagodont objections. A new species of Peradectes from
the Paskapoo Formation of Alberta (Paleocene) is set to
join the chorus of dissent, as it also wears evidence of these vacuities.
Sex?
It's also been suggested that E. browni and E. cutleri might like to breed;
they may be members of complementary sexes rather than distinct species. However, the further
enlargement of the premolars of the latter suggests some kind of dietary specialisation.
Male and female mammals are built somewhat differently (I'm pleased to be able to confirm),
but this kind of difference would be surprising, and possibly result in chronic arguments
concerning which restaurant to visit. Assuming they were still capable, then a male of one
species and a female from the other, would probably have no interest in mutual rumpy-pumpy.
The species appear distinct.
Lower jaw
The following is based on my reading of Matthew, 1916.
Discovery
"The specimen was discovered by Mr. Barnum Brown while engaged in undermining a
Ceratopsian skull beneath which it lay" (p.483). That might sound a bit like some
form of anti-ceratopsian psychological warfare, but Brown was trying to delicately persuade
the surrounding rock to release the head of a dinosaur.
He was using a precision scientific instrument known as a whopping heavy pick axe. One
blow hit a bonus prize and didn't do much for its integrity. Brown noticed the
Eodelphis fossil just after smashing it. Thus alerted, thorough searching recovered
at least most of the fragments. Consequently, a certain AE Anderson was later presented
with an Upper Cretaceous jigsaw puzzle; a kind of challenge he was particularly adept at
solving. Bits of the back of the lower jaw were absent (much of the coronoid process and
the dentary condyle), but it didn't suffer too badly in the circumstances. The lack of
left-over fragments suggests Brown was able to salvage just about everything.
Remains
Most the left jaw was present and the rear molars were in reasonable condition (p.485). Other
teeth had suffered from corrosion and breakage. A second fragment from the right jaw
contained remains of the incisors and canine. Two pieces of the skull were also available
including the front of the cheek region.
Teeth
Information was restricted to the lower dentition.
Incisors and canine
Three incisors are represented and they range in size from modest to minute. The second
is the biggest of them, but it was much smaller than the canine, which had been reduced to
a stump. All the crowns had suffered badly.
Premolars
No diastemata occur either behind the canine or between
the premolars, so the teeth are tightly packed. The p1 is a rather puny, single-rooted
effort at a premolar, which also couldn't be bothered to retain much of its presumably
uninteresting crown. Number two is larger, double-rooted and made some attempt at having a
small talonid heel. The third was larger still and also
boasted of two roots.
Molars
Preservation improves with some of these teeth, but the first molar follows the more
derelict tendencies of the anterior lot. Not much remains apart from the roots. However,
it was somewhat more fully erupted than the neighbours on either side, and that's the sort
of behaviour expected of an m1.
The m2 is heavily worn by use (p.487). Matthew notes its size and proportions are much like
those of the third molar and he grants the tooth no further comment. Number three is graced with a
trigonid of modest height and an elongated, basined
talonid. Both the paraconid and
metaconid were broken, but what remains suggest they were of much the same height. The
protoconid is relatively low. At the back on the
lingual side of the talonid are found two twinned cusps;
the entoconid and the hypoconulid. The hypoconid is a lower cusp on the
buccal side. A strong cingulum
is located at the rear.
The fourth molar is the best preserved (p.488) and broadly reflects its predecessor, although
it does allow a bit more space between the twinned talonid cusps. The cusps of the
compressed trigonid are also much as mentioned for the m3, but the paraconid is a bit
higher than the metaconid.
Dentary
The jaw is compact in comparison to the Virginian opossum (Didelphis); proportionately
shorter and more robust, with the front ascending more sharply. Holes termed mental
foramina are to be seen beneath the p2 and m1. These are for the passage of unseful wiring
such as nerves.
Holotype
The holotype, AMNH 14169, consists of left and right mandibles
in the collection of the American Museum of Natural History, New York. These came from
Sand Creek Alberta. The specific name honours Barnum Brown, who found the fossil while
digging out a dinosaur skull.
Additional notes
The type-fossils of both species come from the same site and they were at one time held to
be synonymous. This is no longer the prevailing opinion.
|
| Reference: | Matthew (1916), A marsupial from the Belly River Cretaceous
with critical observations upon the affinities of the Cretaceous mammals, Bulletin of the
American Museum of Natural History, 35, p.477-500. |
| Species: | Eodelphis cutleri (Woodward, 1916) Simpson
GG, 1928 |
| Aka: | Boreodon matutinus Lambe, 1902; Cimolestes cutleri
Smith Woodward, 1916 |
| Place: | Upper Oldman Formation, Alberta & Montana |
| Country: | Canada & USA |
| Age: | Campanian, Upper Cretaceous |
| Remarks: |
Additional notes
Gordon, 2003 (p.45) offers a weight estimate of
about 496-544g (m1 only).
Boreodon
This genus was established for a single, not very well preserved
premolar. It's quite large but otherwise uninformative. Fox & Naylor, 2006 refer to
it as a nomen dubium (p.15).
The holotype, should anybody be concerned, is NMC 1887, and it resides in the collection of
the Canadian Museum of Nature, Ontario.
"Probably includes type of "Boreodon matutinus,"from this
locality," (Dr J Alroy). Further, C. cutleri was synonymized with B.
by Sahni in 1972. It was first reassigned to E. by Simpson in 1928.
Sahni, 1972 contains discussion on stagodontid remains from the Judith River Formation,
Montana (p.385-390). He referred some to Boreodon, and considers the history
and scope of that genus. This involves fossils allocated at one time or another to
Eodelphis cutleri (aka Cimolestes cutleri) and E. browni. His
version of Boreodon matutinus included C. cutleri and the alternative
E. cutleri. However, as this view doesn't appear to have withstood the test
of time, I think it sufficient to simply mention that discussion exists. |
| References: | Lambe (1902), New genera and species of the Belly River
Series (Mid Cretaceous), p.79 in Osborn & Lambe (1902), Vertebrata of the
Mid-Cretaceous of the North West Territory, Contributions Ca. Pal., 30, Geological Survey
of Canada. |
| Woodward AS (1916), On a mandibular ramus from an Upper
Cretaceous formation in Alberta, Canada, Proceedings of the Zoological Society of
London, abstract 158, p.30 |
| Genus: Pariadens Cifelli RL
& Eaton JG, 1987
Remarks: The inclusion of this genus in Stagodontidae is tentative, (Cifelli 2004, p.70).
Certainly Fox & Naylor, 2006 don't accept its credentials (p.15). Among other
'defects', the trigonid of the
molars isn't compressed towards the front of the crown, and there's neither a high
paracristid nor a carnassial notch. |
| Species: | Pariadens kirklandi Cifelli RL & Eaton JG, 1987
|
| Place: | Dakota Formation, Utah |
| Country: | USA |
| Age: | Cenomanian, Upper Cretaceous |
| Remarks: | Half a dozen specimens, (teeth), are in the
Oklahoma Museum of Natural History collection. This has been cited as the oldest definite
marsupial genus. Weight estimate ca.
70g (Alroy). A second species is indicated.
Holotype
UCM 54155 is a partial dentary in the collection of the
University of Colorado, Boulder. It preserves three molars,
and these have been designated m2?-m4?. |
| Reference: | Cifelli & Eaton (1987), Marsupial from the earliest Late
Cretaceous of Western U.S. Nature 325, p.520-522. |
| Species: | Pariadens mckennai Cifelli RL, 2004 |
| Place: | Cedar Mountain Formation, Utah |
| Country: | USA |
| Age: | Albian-Cenomanian, Lower-Upper Cretaceous |
| Remarks: | The following is based upon my reading of Cifelli,
2004.
The number of specimens for this species is limited to three lower
molars obtained from one site, (p.70). The
talonids are narrower than known from P. kirklandi,
(especially on the m4), and there's a greater height differential between
trigonid and talonid. This is the largest of the
Mussentuchit metatherians and compares in size to
Turgidodon praesagus. With exceptions as listed in the paper, the molars are
much like those of the younger P. kirklandi. The variation of relative height of
the paraconid and metaconid on different molars, (subequal on m1 but with a taller paraconid
on m4), is consistent with both that species and genera such as
Eodelphis, Didelphodon and the
boreosphenid
Kielantherium, (p.72). A number of details hint at possible affinities with
the later occurring stagodontids, but the referral is tentative.
Holotype
The holotype is OMNH 33072, a left lower molar (m4). It lives in the Oklahoma collection
and the species name honours Malcolm C McKenna, in recognition of his work on the history
of mammals.
Additional notes
Fox and Naylor, 2006 appear unconvinced that this species is part of the genus, and see no
particular connections with stagodonts. A special mention is reserved for the hypoconulid
and entoconid cusps of the talonid, as they couldn't even
bother being twinned. These authors publicly humiliate the animal as "P. mckennai"
and observe: "... it seems best classified as incertae sedis among therians of
tribosphenic grade" (p.15). That suggests
doubts as to whether it's even a metatherian. |
| Reference: | Cifelli (2004), Marsupial mammals from the Albian-Cenomanian
(Early-Late Cretaceous Boundary, Utah, Chapter 5 of Bulletin of the American Museum of
Natural History, 285, p.62-79. |
| Other reports:
Straight Cliffs Formation, Utah
A stagodontid is mentioned from this Santonian location by Eaton JW, 2005.
Link:
Santonian mammals from southern Utah..., Eaton JG, 2005
http://gsa.confex.com/gsa/2005RM/finalprogram/abstract_86565.htm
An abstract from the 57th Annual Meeting of the Rocky Mountain Section.
Gurilliin Tsav, Mongolia
The presently undescribed 'Guriliin Tsav skull' could perhaps represent a Mongolian
stagodontid, (Kielan-Jaworowska et al, 2003 (p.277). |
A. Stagodontidae B.
Pediomyoidea
| Taxon: Pediomyoidea Simpson, 1927
Reference: Simpson (1927), Mammalian fauna of the Hell Creek Formation of Montana,
American Museum Novitates, 267, p.1-7.
Remarks: Simpson established the subfamily of Pediomyinae in 1927. Eighty years later
Davis established the rank of a superfamily for the concept. Hopefully, my usage
on this directory is somewhere approaching consistent.
The following is largely based upon my reading of Davis, 2007. This will necessitate
a considerable amount of rewriting and bookkeeping adjustments, so I hope I don't
up too many screws. A link to that paper is available below.
Until this study appeared, my coverage of pediomyid marsupials reflected my reading upon
these mammals; lots of names but little understanding. I happened to know Brian
Davis was working on a revision, as he'd cited that intention in an abstract from
2004. He appears to have done a fine and much appreciated clean up of the North
American Cretaceous members. However, before getting too involved with that, I think
it'd be good manners to begin as simply as practical by, at first, avoiding funny
anatomical language. For a start, let's call them pedis.
A straightforward introduction to pedis
Pedis were ancient marsupials and, during the
Upper Cretaceous, they were rather popular members of the North American wildlife.
Later, having gone drastically out of fashion in their original homelands, their
descendants spent some time exploring bits of South America. However, remains from
those latter escapades aren't exactly common. They were fairly minor members of
their contemporary communities, and probably not ancestral to any of the marsup
marvels of today. Every pedi that ever padded around on the Earth appears to have
been dead for tens of millions of years.
RIP pedis.
Giant pedis could reach up to modest sizes of something like squirrel-dimensions.
Some may even have been a bit larger than that, but not by much, and most were
considerably smaller. The evidence provided by their teeth indicates a fondness
for suitably sized portions of meat. However, in contrast to many of their
ancestors, pedis inherited some dental specialisations. The most significant of
these inevitably requires several weird words concerning how they cut up their food.
Rather than perservering with the traditional prevallum / postvallid approach,
pedis were converts to a postvallum / prevallid system. Should anybody know of a
way of translating that into accessible English, then please feel free to forward
suggestions. In the meantime, suffice it to say that their teeth sliced up yummy
stuff using somewhat eccentric strokes.
Should you be an individual with certain interests, you might now wish to see
pictures of naked pedi bodies; legs, hips, shoulders, breasts and, perhaps, pleading
and yearning mouths and eyes. You might want pedi porn. While plenty of sex adds
greatly to the appreciation of mammalian activities, the state of the fossil record
could result in disappointment in this instance. The pedi-story, at its most
explicit, is presently written with some scraps of jaw and lots of isolated teeth.
The parents of the owners undoubtedly got on down, grooved and screwed with gusto,
but action shots haven't yet been found for these activities. Still, there's no
reason why you shouldn't pretend to be a pedi with an appropriate partner, should
the opportunity arise. Mind you, should you mention such intentions, it's possible
that your potential partner might leave you alone.
Pedi problems
All pedis shared certain dental characteristics, and these were inherited from
ancestral pedis. Such refinements have been used in efforts to reconstruct pedi
systematics; who's in the family, who's not and which is most closely related with
whom. However, there are several factors acting as mischievous gremlins. Firstly,
the fossil record can be difficult to hear with clarity. Large chunks are missing,
and the remnants can be severely scratched. Play a Beach Boys' LP in a similar
state of preservation and Good Vibrations may sound even odder than it originally
did. Secondly, there are the playful tendencies of convergence. Similar structures
can arise in independent lineages. Merely because some critter has a number of
pedi-like traits, that doesn't necessarily make its owner part of the family. Such
factors make difficulties for cracking the systematic puzzles in many lineages of
animals.
Everybody who cared knew pedi systematics weren't satisfactorily clear. The genus
of Pediomys developed into being a bit of a mess. It contained species which
didn't actually belong in the same genus. However, unless you're in a position to
provide diagnostic traits that rationally allow the basis for a separate
taxon, then it's considered good practice to leave a
single messy genus rather than a larger number of poorly defined ones. Even if you
can't tidy things up, often due to insufficient evidence, then somebody else could
be able to do so later. Furthermore, the family was disreputable. It contained
genera which didn't all stem from one unique common ancestor. Both the genus and
the family were, to use another rude word, polyphyletic.
Should somebody be unclear as to what that means, then suffice it for the while to
say that it's bad. We don't like polyphyletic assemblages. We boo, stick our
tongues out and throw rotten tomatoes at them. They're smelly. We want to see
monophyletic taxa; a single ancestor and all
of its descendants. Still, polyphyletic ones can be more useful than a tangle of
poorly founded genera. A household with no litter bins is likely to be unbelievably
squalid. The objective of Davis was to remove the smell from at least the North
American Cretaceous pedis.
In out, in out, shake it all about
A genus called Iqualadelphis had been
assigned to Pediomyidae, but the results of this study suggest it doesn't belong
(p.217). I've followed that conclusion. Also not within the family are
Aquiladelphis and
Glasbius. However, they are thought to be members of the same
superfamily. A supposed species of the Pediomys genus, "P."
exiguus, doesn't appear to have any particular affinities with the strictly
defined family, let alone that genus. It was transferred to a new taxon:
Apistodon. The ejection of those
critters resulted in the recognition of a
monophyletic family, and the reassignement of a number of other "Pediomys"
species to new pedi genera left a well-grounded genus. However, as stated, this
bout of housekeeping only applied to the known members of the North American
Cretaceous. The relationships of later possible pedis weren't assessed.
Background
Prior to this bout of changes launched by Davis, "Pediomyids" had been an informal
assemblage of diverse and numerous
marsupial mainly from the Upper Cretaceous of North America. Indeed, they were
the most common mammals at some locations. They became extremely rare beyond the
Cretaceous, although a possible member has been reported from the Upper Eocene of
Texas. Relationships may also exist with some Paleocene South American marsup
lines. Typical fossils are isolated teeth with, in some cases, fragments of jaw.
Bits of toe bones have been tentatively referred to these critters from the Lancian
and "Oldman" Formations of North America. However, until more complete remains are
known, such referrals can be no more than tentative.
Presently, and again in the absence of fuller specimens, the diagnoses can't be
based on anything other than characteristics of teeth; most particularly the
molars. Specialities for the uppers include a reduction in size at the front of the
stylar shelf, and the reduction (or complete loss) of a thing known in the trade as
the stylocone. This cusp, alternatively known as stylar cusp B, is (or would be) the
second foremost in a series of cusps occupying the stylar shelf on the
buccal flank of an upper crown. A characteristic
cited for lower molars is perhaps even more obscure, and this concerns ridges
(cristids) towards the rear. The cristid obliqua is buccally positioned from a
notch on the protocristid. If those funny terms seem too frightening to remember,
then not trying to keep them in mind is a viable option. Even so, let's risk a
brief attempt at bringing some sense to this stylar shelf thing on an upper molar.
The poker player's guide to a few upper molar points
There is an item which is absolutely essential for anybody wishing to gain an
appreciation of typical therian upper molars, and
specialists term it the ace of hearts. Ideally, this card should contain a fairly
elongated heart symbol. At the top are a couple of lumpy bits, and I like to think
of those as being tempting items partly exposed to view by a low cut dress. Trying
to drag my attention back from such thoughts, that shape's not a bad representation
of the buccal side of a therian upper molar; the so called stylar shelf. It's got
two lobes with a bay inbetween, and that embayment can be termed an
ectoflexus. Take another quick look at either
the ace of hearts or your beloved's cleavage from the
occlusal perspective (if appropriate). Front lobe, bay, rear lobe. Keep that in mind
and you've got a fine grasps of the breas... a stylar shelf.
Various cusps can occur along this shelf; up to five of them. Sometimes, these
received descriptive names in accordance with their relative positions compared to
other features. For example, the foremost gets called the parastyle. This is
because it's about in line with a main tooth cusp called the paracone. (At least, I
assume that's why.) However, unless it's clear that one of these stylar cusps in
such and such a position resulted, in all cases, from a unique evolutionary event,
then using the same name in each instance could actually prove misleading. To
safeguard against such things, some authors prefer to neutrally term these things
A-E.
Pedi upper molars have fewer cusps on their stylar shelves: typically three. Cusp B
(stylocone) had been dispensed with. Additionally, the front lobe of the stylar shelf
had been reduced in size. Other upper molar specialisations included the strengthening
of a ridge termed the postmetacrista (a crista behind the metacone) and, towards the
lingual side of the crown, an expansion of a major
cusp called the protocone. That's towards the narrower bit of our elongated heart
shape. You might like to keep that ace up your sleeve for either later reference or
cheating at cards.
Pedi nomenclatural developments
Marsh established the genus of Pediomys in 1889 (p.219), and this kindness
was performed for an upper third molar from Wyoming's Lancian Formation. He named
the species P. elegans. It happened to be very small compared to other
mammal fossils he had available. A larger critter was named Protolambda hatcheri
by Osborn in 1898. This, from the same formation, was then transferred to the first
genus by Simpson in 1927, and he established a subfamily for them in 1927. GGS also
added further genera of, what he regarded as, very basal
didelpids (possums). Those turned out to be either synonyms or non-pedis.
With a series of studies ranging from 1964-1973, Clemens revised the situation. The
pedi subfamily was promoted to the rank of a family containing but one genus.
However, he increased the number of species to five. He also speculated upon the
likely characters for the ancestral stock of pedis, at least with regard to their
upper molars. This picture is still generally accepted. There was presumably a
forerunner possessing an Alphadon-like
dentition; a wide stylar shelf with five cusps. The front lobe of the shelf and the
stylocone on it, cusp B, became reduced in size (p.220). This was less pronounced
for "P." elegans than the other species. Clemens also realized that this
"genus" probably contained members of several genera, but it wasn't clear how they
could be securely differentiated.
"Pediomyids" spread from Wyoming to Alberta in 1969, although those additional
fossils were still of a Lancian age. However, earlier remains were then recovered
from the Milk River Formation of Alberta, and these are now thought to date from
the Upper Santonian. Three new taxa were set up by Fox in 1971. "P." exiguus
was held to be the smallest known species and, rather in line with expectations and
chronological concerns, the upper molar morphology seemed somewhat basal for pedis.
Stylar cusp B (stylocone) was large. This cusp was also present for two species of
a new genus, Aquiladelphis. A. incus and
A. minor were larger, closer in size to "P." hatcheri and "P."
florencae, and more clearly pedi-like in build. Subsequently, Fox himself stated
that his "P." exiguus wasn't actually pedi-like at all.
Further pedi species were proposed during subsequent years; for example, "P."
clemensi from the Campanian Judith River Formation of Montana. In 1987, a new
genus from Alberta, Iqualadelphis,
was accused of approximating the ancestral pedi condition and, to make matters more
exciting, possibly also that of primitive marsupials in general. The upper crown is
wide, stylar cusp D strong, and stylar cusp C absent. In contrast to typical pedis,
however, the front lobe of the stylar shelf is stronger and cusp B (stylocone)
distinct. Relatively easy to grasp is that the author responsible, Fox again,
concluded that the Pediomys "genus" contained members of separate genera and,
without specifying precisely what these were, pointed to three lineages (p.221).
Among other things, this was partly based upon the presence or absence of a stylar
cusp in the C position.
Also of relevance to Davis' study is a poorly understood, more basal North American
marsup named Glasbius. While not being a pedi as
such, it may be a relative.
More recent discoveries conspired to alter the understanding of basal marsup upper
molars. Kokopellia is older, and
doesn't accord with pedis or the apparently more basal alphadontids. The front
lobe of the stylar shelf is wide and houses only two cusps; A (parastyle) and B
(stylocone). A cusp in the C position developed at a later evolutionary stage, and
not necessarily only once. Therefore, its absence or presence alone don't isn't
necessarily informative about relationships. Such a feature actually seems to have
come and gone on a number of occasions, and that places a limit upon its diagnostic
utility.
Brief interlude
As we're coming towards the end of this rather lengthy ramble, readers are invited
to obtain a sustaining cup of tea before entertaining themselves with the final
couple of paragraphs. I've just fetched one myself.
Davis, 2007 -the scope
This study took 22 taxa into account (p.222). They included representatives from
all known Upper Cretaceous North American marsup families. All potential NAm pedis
were invited, with the exceptions of two poorly preserved specimens from New Mexico;
Aquiladelphis paraminor and "Pediomys" fassetti. That pair were
treated as synonyms of A. minor and "P. prokrejcii respectively,
seeing as the cited distinctions didn't bear up to scrutiny. Two unnamed taxa were
also invited to participate in the festivities.
57 morphological characters came into consideration. While it could be thought that
these show an unhealthy obsession with molars, especially uppers, this has much to
do with what the fossil record happens to have made available, and where distinctive
features can be found (p.223).
Pedis and their allies
The most basal metatherian among the sampled taxa
was found to be Kokopelli's pet (Kokopellia).
It was followed by five lineages represented (in the sample) by single taxa. That
lot included Eodelphis (a stagodontid),
Iqualadelphis and "P." exiguus.
Two clumped groups followed in the procession. The first consisted of
alphadontids; species of both Alphadon
and Turgidodon. The next branch
identified contained proper pedis and their allies, and this received the status of
a new superfamily, Pediomyoidea. Included are representatives of three related
families; Pediomyidae, Aquiladelphidae (new taxon) and Glasbiidae. Additionally,
new genera were established for some species formerly referred to Pediomys.
Hopefully, this structure is now at least correctly followed by these directories
although, as it's necessitated much tinkering around, I may have screwed up somewhere
along the line. This section should now be termed Pediomyoidea whereas, previously,
it was named Pediomyidae. Some taxa once listed here have been moved to more
appropriate places, and such changes have (I hope) been noted by the site
typist.
And finally, Pediomyidae
Comments in the next paragraphs are restricted to the family, not the superfamily.
Having thrown out "P." exiguus, Davis was left with nine referred species
(seven named and two unnamed ones) that have numerous characteristics in common,
and this appears to have resulted from common descent (p.224). These concern dental
specialisations. The main mode of shearing foodstuff became postvallum / prevallid.
Furthermore, both the upper molar protocone and the corresonding lower molar
talonid basin increased in size, and this enhanced
crushing abilities.
While better crushing is accessible enough, postvallum / prevallid shear is more
esoteric and, as said, if somebody could provide a generally comprehensible
explanation, then that'd be most welcome. For the while, suffice it to say
that these critters were predominantly cutting their food with a
derived form of power stoke prior to chewing it.
This contrasted with the traditional approach.
Nine species show the derived traits required for membership of the strict pedi
club, and these are diverse enough to prompt separation into three related
genera. Although two of these are new, the species concerned had already been
established by previous authors. A transferral to a different genus provides no
reason to alter established specific names. Now, where did I leave my tea?
Additional notes
In the originally available study by Davis there was an error. He kind of
accidentally established a genus called Aletridelphys. This came about by
overlooking the priority due to Protolambda Osborn, 1898. That concept,
previously regarded as a junior synonym of Pediomys, suddenly returned from
the taxonomic grave on account of its original species, Prot. hatcheri,
receiving transfer papers to a separate genus; Protolambda and not the
unnecessary (but cute) Aletridelphys. What a pity. My translation of the
latter name turned out as 'corn-grinding-slave womb'.
A bite sized bit on molars
The molars of Pediomys and
Aquiladelphis are specialised, (Kemp 2005, p.198). Uppers have reduced
stylar shelves with a large trigon basin. The talonid basin on
lowers is similarly enlarged. This produced an increase in grinding ability at the
expense of cutting.
Genera: Aletridelphys (= Protolambda),
Aquiladelphis, Glasbius,
Leptalestes, Monodelphopsis,
Pediomys, Protolambda,
Synconodon (= Protolambda), other reports
Time-Line:
Paleocene: Monodelphopsis, Pediomys?
Upper Cretaceous: Aquiladelphis, Glasbius, Leptalestes,
Pediomys, Protolambda |
| Genus: Aquiladelphis
Fox RC, 1971
Family: Aquiladelphidae Davis BM, 2007
Remarks: The following is largely based upon my reading of Davis, 2007.
Davis sees aquiladelphids as being a family within a grouping called Pediomyoidae
(p.243). As well as being difficult to spell, that concept presently includes two
other (naturally related) families: the pediomyids and the glasbiids. The aquilads
and glasbis are monotypic; a fine word indicating that each plays host to but a
single genus. The pedis are more diverse than that.
Many earlier authors included the aquilads as pedis themselves, and they do appear
to be allies. Three species have been proposed over the years, but Davis
stamped one of them to death. He couldn't see any crucial differences between
A. minor and A. paraminor, and concluded the latter was but a junior
synonym. (Update: A further species, A. laurae, was found hiding in Utah
in 2006. That brings things back to a trio.)
Aquiladelphids were among the largest known mammals from thier time of Earth, but
they were still rather modest members of the fauna. Their teeth could've been
well used for crushing in shells, so called durophagy, in efforts to rudely evict
their inhabitants. However, without checking the stomach contents, such tastes
amount more to a possibility than a kosher rule of diet. Regardless of the small
print on the actual menu, and similarly as known from their glasbiid cousins and
contemporary stagodontids, strong cusps and
shallow, widened basins on teeth were features capable of doing good service in the
crushing business. Imagine the pain inflicted on your finger by a vice-like
device fitted with vicious studs and pits, and the feelings of vigour as your skin
gets punctured, and then the pleasures as your bones start to...
Quite...
The stylar shelves of upper molars boasted of an impressively sized cusp in the C
position, and this contrasts with the situation for other pedimyoids (p.244). As
with pedimyids (the strictly defined family), the front lobe of that stylar shelf
is reduced in size. However, still present is a stylar cusp B (stylocone) although,
in many cases, it had actually split into a pair of fairly wide cusps. The
preparacrista ridge is strongly developed, and the paracone is taller than the
metacone. As with stagodontids and Protolambda,
the final lower premolar is inflated.
... and the invigoration prompted by the cracking noise as the bone begins
fracturing...
| Reassigned species: Aquiladelphis paraminor Rigby JK & Wolberg DL, 1987 see
A. minor | |
| Species: | Aquiladelphis incus Fox RC, 1971 |
| Place: | Milk River Formation, Alberta & Colorado |
| Country: | Canada & USA |
| Age: | Santonian, Upper Cretaceous |
| Remarks: | Davis, 2007 (p.245) implies this was a
large thug of a species with broad lower molars.
Holotype
The type fossil, UALVP 5522, is a fragmentary left upper molar (M3) working at the
University of Alberta.
Additional notes
The holotype’s a student at the Alberta
University. Reportedly, on page 163 of the publication, the name Albertatherium
incus appears, directly above a plate showing Aquiladelphis incus. I've
no idea why. (With thanks to Vince Ward.) |
| Reference: | Fox (1971), Marsupial mammals from the early Campanian Milk
River Formation, Alberta, Canada. In Early Mammals. Edited by Kermack DM & Kermack KA,
Zool. J. Linn.Soc. Suppl. 1, vol. 50, p.145-164, 6 pls. |
| Species: | Aquiladelphis minor Fox RC, 1971 |
| Aka: | A. paraminor Rigby JK & Wolberg DL, 1987 |
| Place: | Milk River Formation, Alberta & San Juan County, New Mexico |
| Country: | Canada & USA |
| Age: | Santonian-Campanian, Upper Cretaceous |
| Remarks: | Davis, 2007 spills more gossip (p.245).
As the specific name indicates, this species was smaller than A. (killer)
incus. The upper molars have a pair of stylar
cusps in the B position, and a large C cusp. However, D is the biggest in the crew
while E is piddling (ie. small, not urinating as in some English usages).
The remains from Alberta's Milk River are Aquilan in age, and this probably equates
to the upper parts of the Santonian. Sparser fossils from New Mexico's Fruita
Formation are somewhat more recent (Judithian -p.247).
Holtypes
UALVP 5539 is a right upper molar now studying at the University of Alberta.
The type fossil of A. paraminor was in the collection of the New Mexico
Museum but, the last I time I heard, it couldn't be found. It's friends roamed the
galleries and corridors yelling: "Where are you, NMMNH P-27706 (formerly UNM
B-5542)?" But answer came there none.
Additional notes
The New Mexico material is Campanian, as far as I'm aware, but present research
indicates the Milk River Formation is probably a bit older than that. An estimate
of bodyweight is about four mice, (100g). |
| References: | Fox (1971), Marsupial mammals from the early Campanian Milk
River Formation, Alberta, Canada. In Early Mammals. Edited by Kermack DM & Kermack KA,
Zool. J. Linn.Soc. Suppl. 1, vol. 50, p.145-164, 6 pls. |
| Rigby & Wolberg (1987), The therian mammalian fauna
(Campanian) of Quarry 1, Fossil Forest study area, San Juan Basin, New Mexico. Geolog. Soc.
of America. Special Paper 209, p.51-80. |
| Species: | Aquiladelphis laurae Eaton JG, 2006 |
| Place: | Cedar Canyon, Utah |
| Country: | USA |
| Age: | Upper Cretaceous |
| Remarks: | Thanks are due to Dino Hunter for uploading the
information. A copy of the paper would be much appreciated. I'm also after:
Eaton, J. F., 2006, Santonian (Late Cretaceous) mammals from the John Henry Member of the
Straight Cliffs Formation, Grand Staircase-Escalante National Monument, Utah, Journal of
Vertebrate Paleontology, 26(2), p.446-460. |
| Reference: | Eaton (2006), Late Cretaceous mammals from Cedar Canyon,
Southwestern Utah, (In) Late Cretaceous Vertebrates from the Western Interior, Lucas SG &
Sullivan RM (Eds.), New Mexico Museum of Natural History & Science, Bulletin 35,
p.373-402. |
| Genus: Glasbius Clemens,
1966
Family: Glasbiidae Clemens, 1966
Remarks: This is an enigmatic genus of unclear affinities. Davis, 2007 placed it
within the superfamily of Pediomyoidea. It's also been referred to
Polydolopimorphia (eg. Case et al, 2004). Presently, I'm following the conclusions
of the more recent of those two studies.
Welcome to the family
According to Davis (p.247), this family contains but one known genus and, as a matter
of fact, nobody's ever disagreed with that. It's the affinities that aren't
overly clear. One problem is a complete absence of any viable candidates as
ancestors. Relevant fossils appear (and stop) abruptly during the Maastrichtian;
the final curtain call of the Cretaceous. A not necessarily vindictive whispering
campaign has voiced the possibilities of Glasbius being part of an
immigrant lineage from somewhere or other, or perhaps having connections with South
American marsups; eg. the subfamily of Caroloameghiniinae or the wider grouping of
Paucituberculata. The reliability of such rumours isn't helped by the chronic
(perhaps total) shortage of South American marsup fossils dating from prior to the
Paleocene.
However, such apparent connections could simply be similarities brought about by
playful parallelism. Molars are of a style called
bunodont and, in itself, this isn't overly instructive with regards to relationships.
Bunodont molars have frequently erupted independently of each other. There's also
an added eccentricity. The fourth molar is radically reduced in size. Among
Cretaceous metatherians a similar reduction is
otherwise only known from some deltatheroidans,
assuming they actually qualify as metatherians. Those animals are best known from
the Campanian of Mongolia, but sparse remains have been picked up in North America.
However, those delta-critters lack typical marsup dental traits and only get
referred to as marsupials in some sloppy press reports.
Glasbius
The main cusps of upper molars are unusually low, and the metacone is higher than
the protocone. Stylar cusp B is a large cusp along the whole molar series whereas
D exhibits more variable habits. It's higher than B on the first pair of molars,
shrinks on M3 and absconds entirely from the final tooth. The other stylar cusps
are either small or, sometimes for C, absent.
Lower molars have the m2 as the longest in the set.
Talonids are generally wider than trigonids,
although this isn't the case for m4. Height differences between the talonids and
trigonids aren't substantial. The premolars, all
of which are double-rooted, increase in size along the line from p1 to p3. |
| Species: | Glasbius intricatus Clemens, 1966 |
| Place: | Lance Formation, Wyoming |
| Country: | USA |
| Age: | Maastrichtian, Upper Cretaceous |
| Remarks: | Weight estimate of 49-60g,
(Gordon & Cifelli 2003, p.95).
"The placement of a species such as Glasbius intricatus, which has
molars that are strikingly similar to those of the
modern marsupials Caluromys philander and C. derbianus, is a strong indication that
this Lancian species probably had a very similar diet as Caluromys. By the Late
Cretaceous, angiosperms had become the most diverse group of plants (Wing and Boucher,
1998), with the appearance of nuts and drupes in the Campanian and Maastrichtian (Friis
and Crepet, 1987). With tooth morphology that is very similar to Caluromys, as well
as the increased dominance of angiosperms as a newly available food source, Glasibus
may represent the first early trend toward frugivory", (Gordon CL 2003b, p.159).
Remains include both upper and lower jaw material and teeth, (Kemp 2005, p.197).
This genus has previously been placed within Paucituberculata Ameghino, 1894.
Holotype
UCMP 48047 works at the University of California, Berkeley. |
| Reference: | Clemens (1966), Fossil mammals from the type Lance
Formation, Wyoming, Part II, Marsupialia, University of California Publications in
Geological Sciences, 62, p.1-122. |
| Species: | Glasbius twitchelli Archibald JD, 1982 |
| Place: | Tullock Formation and upper Hell Creek Formations, Montana &
Frenchman Formation, Saskatchewan |
| Country: | USA & Canada |
| Age: | Maastrichtian, Upper Cretaceous |
| Remarks: | This entry could be improved if a copy of
the paper arrived.
In the meantime, some information has turned up from Lofgren, 1995. He was writing on the
geology and fossils from the Cretaceous-Paleocene transition at Cretaceous-Paleocene,
McGuire Creek, Montana.
Some of the specimens Lofgren had came from Paleocene rather than Cretaceous localites
(p.104) but, in all cases, these were recovered from watercourse channels which dug down
into older, fossil-yielding strata, and probably caused reworking. The species hadn't been
otherwise found beyond the Cretaceous. In reality, the evidence for it having survived
the K-T extinction party(s) isn't convincing.
One difference between this species and G. intricatus is easy enough to grasp.
This critter was bigger. There are also distinctions regarding the presence or absence of
stylar cusps on upper molars. For this species, M2 and M3
never have a cusp in the C position, and M3s wouldn't dream of having any more than a
single cusp at position D. Of lower molars, m2 always has one cingulum cusp and m3 insists
upon two.
Postcanine lengths
Samples from McGuire Creek localities had the following lengths.
Uppers: M2 (3 specimens) 2.31-2.53mm; M3 (2 sp.) 1.78-1.93. Widths are always greater
than lengths for upper molars.
Lowers: p3 (1 specimen) 1.53mm; m2 (3 sp.) 1.98-2.29; m3 (3 sp.) all 2.10; m4 (1 sp.)
1.55. Lower molar lengths are greater than widths. Excepting for the final molar,
talonids are wider than
trigonids.
Holotype
UCMP 115853, an isolated third upper molar, performs before delighted audiences at the
University of Minnesota, in Menneapolis.
Additional notes
Might be reworked Paleocene (unsourced). Weight
estimate of 72-95g, (Gordon & Cifelli 2003, p.95). |
| Reference: | Archibald (1982), A study of Mammalia and geology across the
Cretaceous-Tertiary boundary in Garfield County, Montana. Univ. of Calif. Publ. Geol. Sci.
122 xvi, 286 pp. |
| Genus: Iqualadelphis Fox RC, 1987
Remarks: Sometimes regarded as a pediomyid, this entry has been relocated to
Iqualadelphis. Davis, 2007 found it
too primitive for the pedis. |
| Genus: Leptalestes
Davis BM, 2007
Family: Pediomyidae
'thin thief'
Aka: Pediomys (partly)
Remarks: The following is based upon my reading of Davis, 2007.
This genus was established for some refugees formally assigned to the then
messy pedi genus of Pediomys. The generic name comes
from the Greek leptaleos - 'thin', 'delicate'. Upper molars are small and
slender.
Distinctions
In contrast to other family members, the bases of the upper molar para- and metacones
are connected (p.235), the cones are small and 'protoconal cingula' are lacking.
Lower molars have trigonids and
talonids of equal widths, paraconids and
metaconids of similar heights (p.236), and the entoconid cusp of the talonid is
small. Derived traits include the near disappearance
of stylar cusp D on third upper molars, the tallness of the postmetacrista ridge and
the wide protocone. These teeth also lack a stylar cusp in the C position.
Overall, features of the molars are primitive for North American
metatherians, but their reputation is enhanced
by some derived traits generally associated with pedis. However, the apparently
'primitive' touches could have been contributed by character reversals in the light
of the pedi specialisations.
Present finds place the genus within the Campanian and Maastrichtian of North
America. |
| Species: | Leptalestes krejcii (Clemens WA, 1966)
Davis BM, 2007 |
| Aka: | Pediomys krejcii Clemens WA, 1966 |
| Place: | Alberta, Saskatchewan & Hell Creek Montana, South Dakota,
Wyoming |
| Country: | Canada & USA |
| Age: | Maastrichtian, Upper Cretaceous |
| Remarks: | Davis, 2007 confides (p.237):
Unlike the other species within this genus, both described and an undescribed one
from St Mary River, the metacone of upper molars is
taller and wider than the paracone. In contrast to ?L. cooki, the cones of
upper molars are weaker and there are no 'protoconal cingula'. Lowers have
talonids and trigonids
of similar widths, as also applies for the meta- and paraconids (p.238).
Securely referred remains for this species are presently resticted to Maastrichtian
strata of North America. However, a lower molar from earlier deposits in Alberta,
the St Mary River Formation, may also belong (p.239).
Holotype
UCMP 51390 is a partial left maxilla studying at the
University of California, Berkeley. It proudly preserves the teeth P3-M3, and was
originally arrested in the Lance Formation of Wyoming.
Additional notes
This is another small critter of 10g (Alroy) or about 25-47g
(Gordon & Cifelli, 2003, (p.96).
Lofgren, 1995...
... described specimens referred to this species collected from McGuire Creek localities
in Montana. Some of the sites were Paleocene in age, but they were presumably reworked
by river channels digging down into Cretaceous rock (p.112). Those molars had the following
lengths:
Uppers: M1 1.54mm
Lowers: m2 1.47mm; m3 1.62; m4 1.63.
The size and lack of stylar cusps in the C position of the upper led to their placement
in this species (p.113). The critter is smaller than ?. L. cooki, whereas
Pediomys elegans has C position stylar cusps on uppers.
(Only one upper could be assigned to a definite position by Lofgren, and he had all the
species just cited within one genus.) Lower molars were much like those described
previously from the Lance Formation. |
| References: | Clemens (1966), Fossil mammals of the type Lance Formation,
Wyoming. Part II Marsupialia. University of California Publications in Geological Sciences,
62, p.1-122. |
| Davis BM (2007), A revision of "pediomyid" marsupials from
the Late Cretaceous of North America, Acta Palaeontologica Polonica, 52(2),
p.217-256. |
| Species: | Leptalestes prokrejcii (Fox RC, 1979)
Davis BM, 2007 |
| Aka: | Pediomys fassetti Rigby & Wolberg, 1987; P.
prokrejcii Fox RC, 1979 |
| Place: | Alberta & Montana, New Mexico |
| Country: | Canada & USA |
| Age: | Campanian, Upper Cretaceous |
| Remarks: | According to my reading of the estimable
Davis, 2007 (p.238), this species, as the name indicates, is very similar to L.
krejcii. Indeed, it's been accused of being a suitable candidate for an
ancestor.
Davis also took a look at fossils assigned to P. fassetti from New Mexico.
At least one of those specimens appears to belong to
Alphadon while others couldn't be
differentiated from this species. Consequently, he found the animal guilty of being
partly misidentified and otherwise a junior synonym. In short, he stamped it out of
existence.
Holotypes
The type fossil, from the Upper Oldman Formation of Alberta, is UALVP 14817. It's
part of a maxilla that was kidnapped by researchers
at the University of Alberta. It came supplied with the first two molars.
The holotype of P. fassetti is NMMNH P-10726, although it was originally
described as UNM B-1734. That one's employed at the New Mexico Museum and hailed
from San Juan County.
Additional notes
Gordon, 2003 (p.45) offers a bodyweight range of 17-39g
(Didelphidae m1 L).
Alroy calculated a wright of around 10g for P.
fassetti. |
| References: | Fox (1979), Canadian Journal of Earth Sciences 16:103.
|
| Rigby & Wolberg (1987), The therian mammalian fauna
(Campanian) of Quarry 1, Fossil Forest study area, San Juan Basin, New Mexico. Geolog. Soc.
of America. Special Paper 209, p.51-80. |
| Davis BM (2007), A revision of "pediomyid" marsupials from
the Late Cretaceous of North America, Acta Palaeontologica Polonica, 52(2),
p.217-256. |
| Species: | ? Leptalestes cooki (Clemens WA, 1966)
Davis BM, 2007 |
| Aka: | Pediomys cooki Clemens WA, 1966 |
| Place: | Scabby Butte & Montana, S Dakota, Wyoming, New Mexico,
Colorado |
| Country: | Canada & USA |
| Age: | Campanian - Maastrichtian, Upper Cretaceous - ?Puercan |
| Remarks: | Davis tentatively referred this species to
the genus in 2007 (p.241).
Although the upper molars possess characters typical
of the genus, some features are atypical (p.242): stronger conules, the presence of
'protoconal cingula', talonids that are wider than
trigonids and, seen from the
lingual perspective, a metaconid which is wider
than the paraconid. These aspects appear to be
more the sort of thing expected by stem-pediomyids rather than full-blown members,
and this is why the referral is tentative.
Time
Judithian: New Mexico
"Edmontonian": Colorado / Alberta
Lancian: Wyoming, South Dakota, Montana.
Sadly, I've forgotten the source of a possible Puercan member. However, don't
ignore the question mark against that. Davis makes no mention of such a
possibility.
Holotype
The type fossil, UCMP 47738, was a former resident of Wyoming. This partial right
maxilla, with the teeth P2-M3, is now pursuing a
teaching career at the University of California, Berkeley.
Additional notes
Weight estimate of 58-83g, (Gordon & Cifelli 2003, p.95,
M1 only). |
| References: | Clemens (1966), University of California Publications in
Geological Sciences 62. |
| Davis BM (2007), A revision of "pediomyid" marsupials from
the Late Cretaceous of North America, Acta Palaeontologica Polonica, 52(2),
p.217-256. |
| Genus: Monodelphopsis
de Paula Couto, 1952 |
| Species: | Monodelphopsis travassosi de Paula Couto, 1952 |
| Place: | Itaborai |
| Country: | Brazil |
| Age: | Upper Paleocene |
| Remarks: | A number of teeth are in the linked collection,
but my Portuguese isn’t terribly reliable. |
| Reference: | de Paula Couto (1952), Fossil mammals from the beginning of
the Cenozoic in Brasil. Marsupialia: Didelphidae. Amer. Mus. Novit. 1567, p.1-26.
|
| Link:
Catálogo de Fósseis - Tipo e Figurados da Colecao de Paleovertebrados do Museu Nacional
/UFRJ
http://acd.ufrj.br/mndgp/tfcat.htm
Specimens from Museu Nacional, Rio de Janeiro, Brazil. |
| Genus: Pediomys Marsh OC,
1889
Family: Pediomyidae
Remarks: Hopefully, the layout of this genus is now following the work of Davis,
2007 although, as that led to numerous housekeeping changes, I may have messed up
somewhere along the line. His findings resulted in a number of transferrals to
other newly established genera. These should have changed this taxon into a
monophyletic one with a much reduced number of species. Some of the following notes
are liable to be out of date. Reassigned species are listed below.
Davis assigned most, but not all, previously established species of this taxon to
the same family (p.229), but there was too much diversity to allow one genus. This
led him to reactivate Protolambda, and
establish Leptalestes and
Apistodon, a non-pedi. In addition, other former taxa were
synonymized.
Pediomys is the most basal known genus within
the newly restructured family, albeit with a much reduced count of species. It was
left with just two, P. elegans and an unnamed colleague from Alaska. As with
other pedi upper molars, the front lobe of the stylar
shelf and its stylocone (cusp B) have been reduced. A difference is the retention
of a stylar cusp in the C position; presumably a primitive trait for pedis marsups.
Other distinctions include a significant difference in height between the paracone
(reduced) and metacone, an accessory stylar cusp located between C and the
ectoflexus, and the lowering of a ridge termed
the postmetacrista (seeing as its a crista behind the metacone).
As for the lower molars, the metaconid is higher than the paraconid, the
talonid is both wider and lower than the
trigonid, and there's a marked height differential
between the entoconid and hypoconid, and this results in a
labial slope for the talonid.
Both species are small members of the family.
Additional notes
According to Ryan et al 1998, (p.130), a left lower molar
of this genus has also been recovered from the Horseshoe Canyon Formation, Alberta, (lowest
Maastrichtian). Details of the paper are in the Bibliography.
Hunter & Pearson, 1996 (p.638-639), refer to this genus as 'Pediomys' and state
it's "probably a polyphyletic taxon", (it contains
species which aren't part of one natural genus). They describe a partial lower jaw bearing
remains of three premolars and two molars. It's from
North Dakota and most like P. florencae. A more precise
diagnosis wasn't possible, because differentiation is presently dependant largely upon
characters of the upper dentition in this group.
Simpson, 1927 briefly mentions an isolated upper molar from
Montana. It's modestly sized and he refers it to the genus. However, that was with the
knowledge that this taxon is a "very convenient
receptacle for upper molars of a more Didelphis-like type as opposed to the
more Didelphodon-like ones." It's still
convenient and isn't a natural genus.
Lofgren, 1995 described specimens then referrable to this genus from McGuire Creek
localities in Montana. When doing so he was aware that a generic revision was being
conducted by Rich Cifelli (p.112) but, as the results of that weren't available, he
couldn't take them into account. He had even less chance with the 2007 work by Davis.
That's the scheme presently being followed here. Lacking a convenient crysatl ball, Lofgren
opted to use Pediomys as then established whilst being aware of inadequacies.
Hopefully, I've managed to distribute his comments to their now relevant
entries.
| Reassigned species: P. clemensi Sahni A, 1972 see
?Protolambda clemensi;
P. cooki Clemens, 1966 see ?Leptalestes
cooki; P. exiguus Fox RC, 1971 see
Apistodon exiguus; P. fassetti
Rigby & Wolberg, 1987 see Leptalestes prokrejcii;
P. florencae Clemens, 1966 see Protolambda
florencae; P. hatcheri (Osborn, 1898) see
Protolambda hatcheri; P. krejcii Clemens, 1966 see
Leptalestes krejcii; P. prokrejcii
Fox RC, 1979 see Leptalestes prokrejcii | |
| Link:
Department of Geology, University of Bristol
http://palaeo.gly.bris.ac.uk/Communication/Lemke/Lemke.html
Patterns and Timing of Dinosaur Extinction. Was the end of the non-birdy dinosaurs as
sudden as some would have us believe? I don’t know. A short consideration based on
evidence from Hell Creek. Featured are Alphadon, Pediomys and what looks
suspiciously like a stray, eighty million year late Allosaurus, (or am I mistaken)?
|
| Species: | Pediomys elegans Marsh OC, 1889 |
| Place: | Montana, S Dakota, Wyoming & Alberta, Saskatchewan |
| Country: | USA & Canada |
| Age: | Maastrichtian, Upper Cretaceous - ?Puercan |
| Remarks: | The following is largely based upon my
reading of Davis, 2007.
Although a smalling, this species is larger than its unnamed Alaskan relative.
Upper molars have large paracones, and that area of
the crown is proportionately wider (p.229). Distinctions also occur on ridges of
the lower molars. The entocristid consistently bears an accessory cuspule, and the
cristid obliqua joins close to the buccal margin of
the protoconid.
While generally basal for a pediomyid, specialisations
of the teeth seem to debar this species as a possible ancestor of other known pedis
(p.230). At least similar fossils from tthe Ravenscraig Formation of Saskatchewan
indicate the species may have survived beyond the K-T extinction event(s), as those
remains are Puercan (lowermost Paleocene, p.231). Broadly similar fossils have also
been reported from a Campanian Formation, Dinosaur Park, although there are several
differences concerning the stylar cusps. That could indicated an earlier generation
of this largely Maastrichtian species or, more probably, a distinct yet closely
related taxo..
Holotype
YPM 11866 is an upper left molar attending Yale University. (Osborn had already
informed me it was an upper -1893, p.323). However, a more informative fossil,
CM 11658, is a partial maxilla preserving the teeth
M2-M4, and it's been rewarded with the status of the neotype. Congratulations upon
that may be proffered at the Carnegie Museum in Pittsburgh. And, if so engaged,
please pass on my regards to Dr Luo. I don't mind mentioning I'm jealous of their
fossil collection. Honestly, it makes you sick. They get all the good stuff and
I'm left with the occasional deceased Guinea girl interred near the compost heap.
When alive, they don't like being called pigs.
Additional notes
According to the Peabody catalogue, at least some material has been
referred to Gypsonictops hypoconus Simpson, 1927, (by Clemens, 1973). This does not
include the resident holotype.
25g (Alroy), or 42-111g (Gordon & Cifelli 2003, p.95).
Lofgren, 1995...
... told tales about fossils of this species from McGuire Creek localities, Montana.
Some of those, and perhaps others from the Ravenscrag Formation could be Paleocene in
age (p.113). However, they might also have been reworked into older deposits by
mischievous river channels muddling things up. McGuire Creek specimen lengths are on
p.113-114.
Uppers: M1 (2 specimens) 2.00-2.01mm; M2 (1 sp.) 2,05mm; M3 (1 sp.) 1,86mm.
Lowers: m1 (4 sp.) 1.92-1.98mm; m2 (3 sp.) 2.05-2.10mm; m3 (4 sp.) 2.14-2.38mm; m4
(4 sp.) 1.94-2.24mm
Upper McGuire Creek molars had well developed stylar cusps in the C position, and that's
a contrast to the similarly sized ? Leptalestes cooki
which, subsequently, got thrown out of this genus. There's a tendency for the D cusp to
be larger for this species but smaller for ?L. cooki. However, it's a
tendency with known exceptions.
Lowers were destinguished from ?L. cooki on the grounds of size, but there's also
some degree of overlap between the ranges. As no upper specimens for that other species
were identified at McGuire Creek (p.115), it would seem reasonable to assume that no lowers
were harvested either. Mostly, the lower teeth came from sites also yielding uppers of
P. elegans. |
| Reference: | Marsh (1889), Discovery of Cretaceous Mammalia. Am. J. Sci.(3)
xxxviii, p.81-92. |
| Genus:
Protolambda Osborn HF, 1898
Aka: Aletridelphys Davis BM, 2007; Pediomys (partly); Synconodon
Osborn, 1898
Remarks: The nomenclatural history is a bit involved, so listen carefully. Osborn
established the genus for Pr. hatcheri, the type species. For much of the
twentieth century that was regarded as a species referrable to a loosely defined
Pediomys, a convenient collecting box for broadly
similar marsups. This rendered the genus unnecessary. However, Davis provided a
review of the situation in 2007, and reached the conclusion that a separate genus
was justifiable for this species and perhaps one colleague. Initially, he
proposed the name of Aletridelphys. That was a mistake.
The problem is that Pr. hatcheri already had a generic name, and this was
kindly provided by Osborn in 1898. Despite having long been disdained as a junior
synonym, and laughed at accordingly, moving the species had the logical effect of
recalling Protolambda back out of the dustbin. Regardless of how attractive
the 2007 suggestion might be, Osborn's effort happened to have priority. According
to the Erratum notice added to Davis' study:
"A .pdf version of my original paper (Davis 2007) was available online through
Acta Palaeontologica Polonica starting on Thursday, June 14th, 2007 until it
was removed on Sunday, June 17th, 2007. A corrected version of this paper replaced
the original on Monday, June 18th, 2007, and is available for download."
Needless to say, I saved a copy before that became clear and missed the subsequent
clarification until early in September. T'is the early bird what catches the worm,
as we say in Dipwytch.
Pity
The unfortunate and extremely rapid eradication of Aletridelphys has deprived
future linguists of much entertainment to accompany the drinks and munchables.
Aletris, for those less than fluent in Ancient Greek, refers to a female
slave who specialized in grinding corn. Delphys, often used for marsup
genera, translates as 'womb'. From this could be obtained 'corn-grinding slavess
womb' or some such, and imagine attempting to convey that phrase in a game of
charades. The mind, and various other body parts, would boggle magnificently.
Alas, this harmless pursuit is now off the agenda.
A bit about the critters
Leaving our presumably attractive slave to recover her dignity for a while,
known members of Protolambda consist of middling to larger sized pedis
(p.232). With regards to their upper molars, the
parastyle (stylar cusp A) is an extremist in terms of its
lingual position, as it finds itself to be in line with the tips of the para-
and metacone. In contrast to many models, the
ectoflexus bay consistently retains its shallow depth along all members of the
molar series from M1-M3, and a ridge known as the preparacrista has almost been
done away with. There is good news, however, for fans of the centrocrista. That
ridge is strong. Furthermore, the paracone cusp is inflated and the trigon basin
is wide.
Lower molars have para- and metaconids of similar heights, and all main cusps are
strongly built. The final upper premolar, known as
P3 by its friends and admirers, is a large tooth.
Doing durophagy?
I don't know about you, but my teeth don't indicate I've got much interest in this
sort of behaviour. Durophagy refers to shell crushing, and that's one use
Protolambda's dentition may have been put to. However, establishing the
security of such a conclusion is rather risky without the availability of stomach
contents. An omnivorous lifestyle is another option.
In any event, these teeth could crush. A main contrast to
Pediomys is provided by the complete lack of any
stylar cusp in the C position on upper molars. The inflation of the third upper
premolar is also of interest, as the same can't be claimed for the lower p3. Both
the equivalent gnashers are enlarged for the contemporary
stagodontid marsups. |
| Species: | Protolambda hatcheri Osborn, 1898 |
| Aka: | Aletridelphys hatcheri Davis, 2007; Pediomys
hatcheri (Osborn, 1898) Simpson GG, 1927; Synconodon sexicuspes Osborn,
1898 |
| Place: | Montana, S Dakota, Utah, Wyoming & Alberta, Saskatchewan |
| Country: | USA & Canada |
| Age: | Campanian - ?Maastrichtian, Upper Cretaceous |
| Remarks: | The following is largely based upon my
reading of Davis BM, 2007. For the eight decades prior to that study, the name
generally used for this taxon was Pe. hatcheri. Davis, however, was able to
show the critter belonged to a separate genus.
A very quick sketch
With the exception of its bigger sister, Pr. florencae, this is a comparative
giant among pedis (p.233). However, that still translates as: a fairly small
mammal. Seen from the buccal perspective, the
metacone of the upper molars is wider than the paracone, and rugiosities don't
occur on the protocone. They do in the case of Florence (aka Pr. florencae).
Type fossil
For reasons I don't know, this species has a lectotype rather than a holotype. As far
as I understand the term, such a specimen is established after an original description
neglected to name a holotype. Anyway, the honour was bestowed upon AMNH 2202, a
fragment of upper jaw employed by the American Museum of Natural History in New
York.
Additional notes
Some material has been reassigned to P. florencae,
(Peabody). Several teeth are residents of the Berkeley collection in California. The
species is also known from a fragment of juvenile upper jaw from the North Horn Formation
of Utah, (Cifelli & de Muizon 1998, p.533-535).
Weight estimate of 161-257g, (Gordon & Cifelli 2003, p.96).
Lofgren, 1995...
... told tales upon teeth gathered from McGuire Creek localities in Montana (p.114).
These were presumably Cretaceous teeth that managed to get reworked into Paleocene river
channels. In contrast to other sites, those river channel ones can contain somewhat
mixed faunas.
Page 115 has him divulging personal information on molar lengths, with one tooth mentioned
for each position listed.
Uppers: M2 3.50mm.
Lowers: m2 3.35mm; m3 3.21mm; m4 4.22mm.
Two uppers were actually found, but only one had bothered to retain its full length. In
both cases there's no stylar cusp in position B (p.116), and C cusps are small. These
points and their size are both in line with this species. Lower molars were much like
those described previously from elsewhere by other researchers. |
| References: | Osborn (1898), Evolution of the amblypods, Part I,
Taligrada and Pantodonta, Bulletin of the American Museum of Natural History, 10,
p.160-218. |
| Davis BM (2007), A revision of "pediomyid" marsupials from
the Late Cretaceous of North America, Acta Palaeontologica Polonica, 52(2),
p.217-256. |
| Species: | Protlambda florencae (Clemens WA, 1966)
Davis BM, 2007 |
| Aka: | Pediomys florencae Clemens WA, 1966 |
| Place: | Wyoming, Montana, North Dakota, South Dakota |
| Country: | USA |
| Age: | Maastrichtian, Upper Cretaceous - ?Puercan |
| Remarks: | Davis, 2007 helpfully provides some
information, as well as a new generic home for this species.
This marsup is the largest known member of Pediomyidae. At least in general, it
roamed around North America somewhat later than its sister, Pr. hatcheri.
The protoconid of lower molars is located further
forward than for other family members.
Holotype
The holotype, UCMP 51440, is a student of The University of California. It's part of a
maxilla containing two
molars (M2-M3). This was recovered from the Lance Formation of Wyoming, say so
Hunter & Archibald 2002, p.198).
Additonal notes
Various specimens hanging out at Yale. Weight estimate of 363-470g,
(Gordon & Cifelli 2003, p.95).
Lofgren, 1995...
... got personal about McGuire Creek specimens from Montana for this species as well.
Again, according to this multifaceted gossip, some were accused of probably being
Cretaceous teeth that managed to get re-deposited into Paleocene river channels. He also
informs me of the large size, and provides lengths for some Montana molars (p.116).
Uppers: M1 (2 specimens) 2.82-3.29mm; M4 (1 sp.) 4.10mm.
Lowers: m2 (1 sp.) 4.13mm; m3 (1 sp.) 5.25mm.
The lower m3 is larger than the only specimen previously described for the species (p.117),
but that could just be individual variation. |
| References: | Clemens (1966), Fossil mammals of the type Lance formation.
Wyoming. Part II. Marsupialia. University of California Publications in Geological Sciences,
62, p.1-122. |
| Davis BM (2007), A revision of "pediomyid" marsupials from
the Late Cretaceous of North America, Acta Palaeontologica Polonica, 52(2),
p.217-256. |
| Species: | ?Protolambda clemensi (Sahni, 1972) Davis
BM, 2007 |
| Aka: | ?Aletridelphys clemensi Davis, 2007;
Pediomys clemensi Sahni A, 1972 |
| Place: | Judith River Formation, Montana & Alberta |
| Country: | USA & Canada |
| Age: | Campanian, Upper Cretaceous |
| Remarks: | Davis, 2007 naturally considers this
species as well. There could perhaps be some conflicts with the information based
on Sahni, 1972 below, but I haven't noticed any beyond the differing generic
referrals. The earlier author used Pediomys in a wider, weakly defined
sense.
Davis' placement of the species in this genus is only tentative, as represented by
the question mark. The closer affinities remain somewhat unclear (p.234). It
qualifies as a pedi and, if a member of Protolambda, then it's a relatively
basal one. It's also smaller than the two other
species.
Relatively speaking, stylar cusp D on upper molars
is set both futher forward of and more buccally from
the metacone (p.235). the postmetacrista is low, and the paracone is wider than the
metacone. While it lacks most specialisations associated with the genus, that isn't
implausible for a basal representative. Specialisations require time to arise and
ripen. In line with other species of Protolambda, both the paracone of upper
molars and the third upper premolar are inflated.
According to Sahni
The following is based upon my reading of Sahni, 1972.
This species is a smalling among smallings, and he found it compared most closely with
the somewhat later Pediomys elegans (p.384). Of the
stylar cusps on the upper molar (which is either an M2
or M3), A and D are well developed, B is rather pathetic and somewhat to the rear of
the paracone level, and C is close and similarly a weakling (although a bit
larger).
Molars
Two labial pieces of upper molars were extracted from
Clambank Hollow, and they're much alike. The non-type specimen differs by a lack of
conules and is slightly larger. The stylar shelf, a feature located to the labial
side of the main crown, is weak and not bilobate (p.385). That means no
ectoflexus bay divides it into two portions, and
this contrasts with various metatherians of the
time. This delightful shelf provided space for a number of cusps and, unlike with
most contemporary metatherians, cusp A is well developed in this instance. As noted
above, B and C are puny attempts, while cusp D is the largest in the gang.
Five lower molars were also discovered and allocated to Pediomys. In part,
this is due to the position of a ridge, the crista obliqua, which adorns the wall of
the talonid basin. In this case, it collides with
the trigonid at the
protoconid, and that's further labial than for most relatives. It is, in short,
a pediomyid trait. The lengths of these molars range from 1.8 - 2.6mm, and that's
comparatively small for the genus.
Holotype
AMNH 77373 is an upper molar in the employ of the American Museum of Natural History,
New York. It came from Clambank Hollow, Montana. The specific name honours WA
Clemens, a good friend of Mesozoic mammals based at the University of California,
Berkeley.
Additional notes
A chubby mouse weight of about 30g
(Alroy), or a chubbier one (Gordon 2003, p.45), 65-76g. |
| References: | Sahni (1972), The vertebrate fauna of the Judith River
Formation, Montana, Bulletin of the American Museum of Natural History, 147(6),
p.321-412. |
| Davis BM (2007), A revision of "pediomyid" marsupials from
the Late Cretaceous of North America, Acta Palaeontologica Polonica, 52(2),
p.217-256. |
| Other reports:
Laguna Umayo, Peru
"An unidentified taxon possibly referable to the
Pediomiyidae has also been reported from Laguna Umayo (Sigé, 1972). This, too, is potentially
important, as the family is otherwise confined to the Campanian-Maastrichtian of North
America (Clemens, 1979)", (de Muzion & Cifelli 2001, p.95). The age assignation
is ?Late Cretaceous. |
| Help:
Should anybody have any further information, I'd be pleased to hear of it.
Regarding references and Bibliography:
I haven't and can't verify all the references, so beware. Traditional papers used in constructing
this page are in the bibliography. If you feel these are too few, then send some more.
With thanks to all the featured sources.
back to top
Trevor Dykes, May 2002. Latest update: 8.5.2008
Ktdykes@arcor.de |
| With further thanks due to:
Weight estimates
Dr John Alroy, North American Fossil Mammal Systematics Database
http://www.nceas.ucsb.edu/~alroy/nafmsd.html
The source of much of the above information, including weight estimates.
Weight estimates have generally, when not otherwise stated, been
shamelessly stolen from John Alroy's internet site. When other sources are available, this
may produce disparities. I've got two comments to offer.
Firstly, if you were to claim that some European hedgehogs (Erinaceus europaeus)
weigh 400 grammes, you'd be correct. If I were to add that some reach 1,2 kilos, I'd also
be correct. Some hedgehogs are bigger than others.
Secondly, the estimates partly depend upon the questions posed. If a calculation is based
upon an insectivore model, the answer may be 50g. Choose a South American opossum, and it'd
perhaps be closer to 150. Think primate, and 300g might result.
A further source is Gordon, 2003 (p.45-46). Cynthia Gordon's research offers various
alternatives. These depend upon which tooth is used, (lower molar 1 or Upper Molar 1),
and which group of animals it's compared to. As they were New World marsupials, I'll
include the range of estimates based upon Didelphidae. These calculations were derived
from a. m1 Length, b. m1 L x Width, c. M1 L and d. M1 L x W.
A third source is Gordon & Cifelli, 2003 (p.93-97). The methods are as for Gordon,
2003.
A rough system of measurement is employed in these directories. A standard mouse = 25g, a
rat counts as 400 whilst a beaver equals about 25 kilos.
The Prehistoric Data Files
http://www.angellis.net/Web/PDfiles/marsups.pdf
A mighty Mesozoic meta-index.
Martin Jehle, Paleocene mammals of the world, Class Mammalia
http://www.paleocene-mammals.de/pal1.htm
This site not only is good, it looks like it too.
John H Burkitt, Mammals, A World Listing of Living and Extinct Species
http://cougarhillweb.org/mammals.pdf
Back on-line.
BIOSIS, The Index to Organism Names
http://www.biosis.org.uk/triton/indexfm.htm
The Society of Vertebrate Paleontology BFV Online, (John Damuth)
http://www.bfvol.org/
The Peabody On-line VP Catalogue
http://george.peabody.yale.edu/vp/
The thrilling animated graphics are courtesy of
HitBox Central,
Animation Library and
best animations.com. |
Bibliography:
Averianov AO, Archibald JD & Martin T (2003), Placental nature of the alleged
marsupial from the Cretaceous of Madagascar. Acta Palaeontologica Polnica 48(1),
p.149-151.
Case JA, Goin FJ & Woodburne MO (2004), "South American" marsupials
from the Late Cretaceous of North America and the origin of marsupial cohorts, Journal of
Mammalian Evolution, 11(3/4), p.223-255.
Cifelli RL (2004), Marsupial mammals from the Albian-Cenomanian (Early-Late
Cretaceous Boundary, Utah, Chapter 5 of Bulletin of the American Museum of Natural History,
285, p.62-79.
Cifelli RL & Muizon de C (1998), Marsupial mammal from the Upper Cretaceous
North Horn Formation, central Utah. Journal of Paleontology, 72 (3), p.532-537.
Case JA, Goin FJ & Woodburne MO (2004), "South American" marsupials
from the Late Cretaceous of North America and the origin of marsupial cohorts, Journal of
Mammalian Evolution, 11(3/4), p.223-255.
Davis BM (2007), A revision of "pediomyid" marsupials from the Late Cretaceous
of North America, Acta Palaeontologica Polonica, 52(2), p.217-256.
Fox RC & Naylor BG (2006), Stagodontid marsupials from the Late Cretaceous of
Canada and their systematic and functional implications, Acta Palaeontologica Polonica,
51(1), p.13-36.
Gordon CL (2003), A first look at estimating body size in dentally conservative
marsupials, p.4-55 (In) Functional Morphology and Diet of Late Cretaceous Mammals of North
America, Ph.D. Dissertation, University of Oklahoma, p.i-xiv and 1-177.
Hunter JP & Archibald JD (2002), Mammals from the end of the age of the
dinosaurs in North Dakota and southeastern Montana, with a reappraisal of geographic
differentiation among Lancian mammals, in Hartman JH, Johnson KR & Nichols DJ
(eds.), The Hell Creek Formation and the Cretaceous Tertiary boundary in the northern
Great Plains: An integrated continental record at the end of the Cretaceous, Boulder,
Colorado, Geological Society of America Special Paper 361, p.191-216.
Hunter JP & Pearson DA (1996), First record of Lancian (Late Cretaceous)
mammals from the Hell Creek Formation of southwester North Dakota, USA. Cretaceous Research
17, p.633-643.
Kemp TS (2005), The Origin and Evolution of Mammals, Oxford University Press,
pp.331.
Kielan-Jaworowska Z, Hurum JH, & Badamgarav D (2003), An extended range of the
multituberculate Kryptobaatar and distribution of mammals in the Upper Cretaceous
of the Gobi Desert. Acta Palaeontologica Polonica 48(2), p.273-278.
Lofgren DL (1995), The Bug Creek Problem and the Cretaceous-Tertiary Transition at
McGuire Creek, Montana, University of California Publications Geological Sciences, vol.
140, 185pp.
Matthew WD (1916), A marsupial from the Belly River Cretaceous with critical
observations upon the affinities of the Cretaceous mammals, Bulletin of the American Museum
of Natural History, 35, p.477-500.
McKenna MC & Bell SK (1997), Classification of Mammals Above the Species Level.
Columbia University Press.
Morgan GS & Lucas SG (1999), Type specimens of fossil vertebrates in the New
Mexico Museum of Natural History and Science. New Mexico Museum of Natural History and
Science Bulletin 16, p.253-259.
Muizon de C & Cifelli RL (2001), A new basal "didelphoid" (Marsupialia,
Mammalia) from the Early Paleocene of Tiupampa (Bolivia), Journal of Vertebrate Paleontology,
21 (1), p.87-97.
Osborn HF (1893), Fossil mammals of the Upper Cretaceous beds, Bulletin of the
American Museum of Natural History, 5, p.311-330.
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